A University of Leeds research team found adding dilute acetic acid – vinegar – to groundwater sites contaminated with harmful chromium compounds boosts the growth of naturally-occurring bacteria by providing an attractive food source.

These then cleanse the affected area by changing the chemical make-up of the compounds to make them harmless.

Dr Doug Stewart, from the School of Civil Engineering, who led the research team with Dr Ian Burke, from the School of Earth and Environment, said: “From the results we have so far I am certain that we can develop a viable treatment for former industrial sites where chromate compounds are a problem.

“As society becomes more environmentally-aware, new regulations demand that past mistakes are rectified and carbon footprints are reduced.

“By designing a clean-up method that promotes the growth of naturally occurring bacteria without introducing or engineering new bacteria, we are effectively hitting every environmental target possible.”

The bacteria reduce chromium from a soluble state to an insoluble one meaning it can be left safely in the ground with no contamination risk to the environment.

Dr Burke said: “The original industrial processes changed these chemicals to become soluble, which means they can easily leach into the groundwater and make it unsafe.

“Our treatment method reconverts the oxidised chromate to a non-soluble state, which means it can be left safely in the ground without risk to the environment. As it is no longer ‘bio-available’ it doesn’t present any risk to the surrounding ecosystem.”

University engineers and environmental scientists are developing methods of helping contaminated water clean itself by adding simple organic chemicals such as vinegar.

The harmful chromium compounds found in the groundwater at sites receiving waste from former textiles factories, smelters, and tanneries have been linked to cancer, and excessive exposure can lead to problems with the kidneys, liver, lungs and skin.

Previously, chromate chemicals have been successfully treated in neutral Ph conditions but researchers say this study is unique because it concentrates on extremely alkaline conditions – potentially much more difficult to treat.

The favoured existing method of dealing with such groundwater contaminants is to remove the soil to landfill, which can be costly and energy inefficient.

Scientists say the methods being developed will allow treatment to take place on site, which is safer, more energy efficient and cheaper.

The research is published online in the Journal of Ecological Engineering at the following weblink.

David Gibbs

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