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Pumping Water from Disused UK Mines

By : Chris Peacock |July 03, 2014 |Blog |0 Comment

In Britain, we have been mining for coal, metal ores and other minerals since the Bronze Age. Now most of these mines have been abandoned, contaminated water is being discharged into rivers and streams. Mines that have closed more recently, are starting to fill with groundwater, which may discharge in the future.

“After a mine closes, you are no longer pumping water out so the water rises within the mine,” said Jeremy Crooks, the Coal Authority’s principal contracts manager, to the BBC.

“It absorbs metals and minerals from the surface of the workings and when they come to the surface they can be released and you can have a highly-polluted water.”

According to Environment Agency: “Nine percent of rivers in England and Wales, and two percent in Scotland are at risk of failing to meet their Water Framework Directive targets of good chemical and ecological status because of abandoned mines.”

So how do we prevent this contaminated water from entering our rivers?

Wheal Jane Minewater Treatment Plant

The Coal Authority manages 51 processing plants across England, Wales and Scotland. They are working to prevent contaminated water from reaching our watercourses. The largest minewater treatment plant in Britain is in Cornwall, once a hive of mining activity. The Wheal Jane water treatment plant prevents 670 tonnes of iron and 150 tonnes of zinc from finding its way into the Restronguet Creek each year. Underground pumps works 24 hours a day, pumping out 110 litres per second and sending the water for treatment.

The acidic water is neutralised by adding lime. A chemical is then added that causes the metal particles in the water to bond together.  The sludge that’s left over is pumped into clay-lined impermeable lagoons and the clean water is discharged into a stream, which then emerges into the River Fal.

Over time, the level of metal contamination will reduce as the water gradually washes away the contaminants from the exposed surfaces of the old mine. It’s believed that the treatment process will have to continue at Wheal Jane for another 50 years. This process costs the government about £1.5 million to run each year.

Environmental Effects of Minewater Discharge

The polluted water can have drastic consequences not just for aquatic ecosystems but the ecology of the river as a whole. Acidic water can kill fish by damaging their gills, and game fish, such as salmon and trout, are unable to reproduce because they need well-aerated, open gravels to lay their eggs in.

The effect of minewater can be seen by the naked eye as the iron present in the water can turn the watercourse red. When water reaches the surface the iron particles oxidise, turning from a ferrous to a ferric state. The ferric hydroxide that forms in the water is known as ochre. In itself, this increases the turbidity of the water, but in the worse cases, the particles can precipitate out of solution and join together to form a substance thick enough to coat river beds with a rusty coloured sludge.

Monitoring Waste Water Treatment Systems

Any water discharged must meet minimum standards as set by the Environment Agency. It is likely that the Coal Authority running the water treatment plants use water testing instruments to monitor not only the quality of the water to be discharged but the quality of surrounding surface water to ensure the plant is working properly.

Aquaread manufactures multi-parameter water monitoring equipment, which can be used for waste water testing. The sort of waste water parameters that may be tested include pH, turbidity, and ORP.

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