Lead pollution is one of India’s most overlooked public health crises. According to a 2020 UNICEF and Pure Earth report, India is home to over 275 million children with elevated blood lead levels, nearly half the country’s child population.
A major source of this contamination is wastewater from battery recycling units, which often carries high concentrations of dissolved lead into rivers and soil.
Now, researchers at the Indian Institute of Technology (IIT) Guwahati have developed a biological process that could offer a cleaner way to deal with this problem.
Instead of relying on chemicals, the team has turned to naturally occurring bacteria to pull toxic lead out of acidic industrial wastewater.
The hidden problem in treating water
The research was carried out by Professor Pranab Kumar Ghosh of the Department of Civil Engineering and research scholar Sreekanth Yadav Golla, with findings published in the Journal of Environmental Chemical Engineering.
The innovation comes amid growing global concern over lead pollution from industrial effluents, which remains a persistent environmental and public health challenge.
Most treatment plants use chemicals to clean wastewater that contains lead. But this process takes time and creates a lot of lead-filled sludge, which then has to be disposed of safely.
This sludge can become another problem. If it ends up in landfills, the lead in it may slowly leak back into the soil and water.
To solve this, the IIT Guwahati team used sulphate-reducing bacteria, a type of microorganism that grows in places without oxygen. These bacteria help turn dissolved lead in wastewater into a solid mineral called lead sulphide. Once the lead becomes solid, it can be removed from the water more easily.
Training bacteria to survive toxic water
Explaining the process, Ghosh said that sulphate-reducing bacteria convert sulphate in wastewater into sulphide, and that this sulphide reacts with dissolved lead to form lead sulphide, a solid mineral that can be easily removed.
He added that the process also reduces the acidity of the wastewater, creating better conditions for the bacteria to survive and improving overall treatment efficiency.
This was easier said than done. One big challenge was keeping the bacteria alive in such toxic water.
The research was carried out by Professor Pranab Kumar Ghosh of the Department of Civil Engineering and research scholar Sreekanth Yadav Golla
Wastewater from battery recycling units is extremely harsh. It is highly acidic and contains heavy metals, making it difficult for most living organisms to survive.
To overcome this, the team developed a method to gradually acclimatise the bacteria to increasingly extreme conditions, essentially training them, step by step, to tolerate the very wastewater they were meant to clean.
The approach paid off. The biological reactor successfully removed lead from wastewater and converted it into stable lead sulphide, enabling continued treatment of the wastewater, while generating less lead-containing sludge compared to conventional methods.
What happens to leftover sludge?
The researchers also had to check whether the leftover sludge was safe to handle. To verify this, the team examined the bio-sludge produced during treatment.
Golla said they examined the bio-sludge to determine its environmental safety, and found that most of the lead in the sludge was present in stable forms that do not easily move or dissolve.
The process takes time and creates a lot of lead-filled sludge, which then has to be disposed of safely.
Leaching tests showed that only very small amounts of lead were released from the sludge, with concentrations remaining below regulatory limits. This matters because it means the treated waste is far less likely to re-contaminate soil or groundwater than sludge from chemical treatment.
Wider applications ahead
The researchers said the process could also be applied to wastewater treatment in mining, smelting and metallurgical industries, all sectors that routinely deal with heavy metal contamination.
Future research will focus on making the process more economical, reducing sulphide levels in treated water, and exploring whether useful metals can be recovered.
If scaled successfully, this bacteria-driven approach could give India’s battery recycling and metallurgical industries a sustainable alternative to chemical-heavy treatment, one that produces less hazardous waste while tackling a pollutant that has quietly affected the health of millions of Indian children for decades.
Images courtesy of IIT Guwahati
