By Sustainability Matters

Engineers in Melbourne have developed a method to remove heavy metals, including copper and zinc, from biosolids.

The environmentally friendly method was led by RMIT University in collaboration with South East Water and Manipal University in India. It recycles the acidic liquid waste that is produced during the recovery phase instead of throwing it away.

Kalpit Shah, lead senior researcher from RMIT, said the metals found in biosolids — treated sewage sludge — can be valuable and the team’s approach can recover metals such as copper and zinc.

According to Shah, the innovation helps ensure that biosolids do not leach heavy metals into the environment, retaining the nutrients that can be used for land applications.

“With further processing, the biosolids can be turned into high-grade biochar, which is a renewable energy resource and has a range of applications including as a fertiliser,” Shah said.

The research is published in the international journal Hydrometallurgy.

The overall metal-removal process occurs over three stages: extraction, purification and recovery. Prior to the team’s work, this had not been fully explored among researchers beyond the first stage.

Ibrahim Hakeem, the first author of the study, said biosolids can contain several metals locked within organic matter, making purification and metal recovery challenging. The new approach can recover metals one by one and is a closed-loop solution with minimal environmental harm.

Abhishek Sharma, co-author from Manipal University, said the work was beneficial for improving the efficiency of the conversion of biosolids to biochar via pyrolysis.

According to Shah, the work complements the team’s biochar-producing technology, which South East Water, Intelligent Water Networks (IWN) and Greater Western Water are trialling at the Melton Recycled Water Plant.

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