Engineers and environmental scientists at the University of Leeds are developing methods of helping contaminated water to 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.
The research team, led by Dr Doug Stewart from the School of Civil Engineering and Dr Ian Burke from the School of Earth and Environment, has discovered that adding dilute acetic acid (vinegar) to the affected site stimulates the growth of naturally-occurring bacteria by providing an attractive food source. In turn, these bacteria then cleanse the affected area by altering the chemical make-up of the chromium compounds to make them harmless.
"The original industrial processes changed these chemicals to become soluble, which means they can easily leach into the groundwater and make it unsafe, says Dr Burke. "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."
Chromate chemicals have previously been successfully treated in situ in neutral Ph conditions, but this study is unique in that it concentrates on extremely alkaline conditions, which are potentially much more difficult to treat.
The current favoured method of dealing with such groundwater contaminants is to remove the soil to landfill, which can be costly, both financially and in terms of energy usage. The Leeds methods being developed will allow treatment to take place on site, which is safer, more energy efficient and much cheaper.
Dr Stewart says: "Highly alkaline chromium-related contaminants were placed in inadequate landfi
|Contact: Jo Kelly|
University of Leeds