Metal removal

A new device, designed to remove toxic metal pollution from water flowing from disused mines in mid Wales, goes on trial this month.

Developed by an international team of scientists and led by researchers at the University of Wales, Aberystwyth (UWA), the BIOMAN (Bioabsorption of metals from abandoned mine sites) water purification system could represent a significant step forward in tackling a world wide pollution problem.

In Ceredigion alone, the UK Environment Agency has identified 38 sites from the worst 50 sites in Wales, where river water quality is significantly affected by pollution from old mine workings.

With the backing of a 1.4m Euro grant from the European Commission, the Aberystwyth team have been working with scientists from Sheffield University and the University of Bologna in Italy to develop and test the technology.

The first prototype unit consists of an average sized loft cold water tank inside which is placed a large tea bag like structure filled with dealginated seaweed, a by-product of an industrial process to make food additives from seaweed.

Key to the process is the dealginated seaweed’s ion-exchange capacity. Initial laboratory tests have shown that dealginated seaweed has the capacity to trap the principal mine water pollutants, in this case zinc, lead and cadmium, as the water flows through the tank.
The project is led by Dr. Bill Perkins from the Institute of Geography and Earth Sciences at UWA.

“A large number of the mines in Ceredigion continue to pollute the surrounding environment many years after they closed – which in some cases is over a 100 years. The problem has not improved over the years and the level of pollution is unlikely to fall dramatically in future – a fact highlighted by the Environment Agency’s report,” he said.

“The principal aim of this project is to develop an effective and sustainable piece of equipment that will remove the toxic materials from the water. Important considerations also include cost, so that the unit is not too expensive and requires relatively little maintenance. Once the field trials have been successfully completed we hope that organisations charged with improving river water quality will adopt it”, he added.

The first prototype, which is set to undergo field trials at three different locations in the Cambrian Mountains of mid-Wales, will treat 1 litre of mine water per minute. A second set of field trials featuring equipment with the capacity to treat 10 litres per minute will start later in the autumn in Wales and in an area of Italy where the predominant metal mined was copper and where the chemical properties of the water are different.

A third generation prototype capable of treating 100 litres per minute, well in excess of the outflow of the majority of abandoned mines in Wales, is expected to be tested in early 2006. This version will feature sensors and a remote computer link that will enable scientists to monitor the effectiveness of the equipment without having to visit individual sites.

“Once saturated, the dealginated seaweed will need to be replaced. The frequency at which this will have to be done will vary from mine to mine according to the concentrations of the pollutants and the rate of water flow,” added Dr. Perkins.

Working with Dr. Perkins are Dr. Nick Pearce and Suzanne Hartley at UWA, Dr. Robert Edyvean from the School of Chemical and Process Engineering at the University of Sheffield and Dr. Enrico Dinelli from the Department of Geo-environmental Sciences at the University of Bologna.