A pilot scheme to clean rivers polluted by abandoned metal mines has delivered "staggering" results, environment officials have claimed.
The new technology - thought to be a world-first - removed up to 99.5% of metals which impact water quality.
The electrochemical technique separated a metallic sludge from mine discharges leaving clean water behind.
Natural Resources Wales (NRW) said it marked a potential "step change" in how the problem is handled.
Metal mining in the UK peaked in the 18th and 19th Centuries and though they have now all closed, their effect on the environment is still obvious.
Wales has more than 1,300 abandoned metal mines, impacting more than 67 water bodies and in excess of 370 miles (600km) of river.
Nine of the 10 worst affected catchments in the UK are in Wales.
The innovative treatment plant has been tested on a stretch of the river Rheidol near Aberystwyth in Ceredigion.
The area is popular with tourists for its scenic reservoir, steam train and red kites, but it was once home to mines producing lead and zinc which now discharge highly acidic, orange water into the river.
It is thought eight tonnes of metal, including zinc, chromium and cadmium, enter the Rheidol every year, spreading out over 11 miles (18km) of river, killing fish and other wildlife.
Since the 1960s the polluted water has been collected in large pools in an attempt to filter out the metals, with limited success.
However, scaling up this technique would require much more land than is available in the narrow, steep-sided valley, so NRW asked technology companies to come up with an innovative solution.
Peter Stanley, a water and land contamination specialist at NRW, said the big advantage of the system it had trialled was that only a "small spatial footprint" is needed.
A portable treatment plant - the size of a car - is attached to a small generator. The system sucks in the dirty water discharged from the mine and passes an electric current through it.
Using a combination of electrolysis and ultrasound it triggers a chemical reaction which removes the heavy metals, adjusts the liquid's acidity and allows clean water to be pumped out and into the river.
The leftover metallic sludge can then be sold or disposed of safely.
"When we've filtered the samples we've been getting 99.5% removal of metals, which is quite staggering," Mr Stanley said.
"I don't know how much more excited I could be in relation to the results that have been shown here - it gives us a new tool in our armour to effect treatment at metal mines, particularly those in steep, challenging environments like this."
Swansea-based firm Power and Water has been granted a worldwide patent for the technology which it hopes to install at other abandoned mines following the success of this trial.
"This week alone we've had interest from consultants working in Sumatra and Australia as well as enquiries about mines in England and Scotland too," said the company's chief executive Gareth Morgan.
"Not only are we looking to try and create a solution that is going to have a beneficial impact on these historical metal mines within Wales itself but the potential to export outside of the country is exciting as well."