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.
Read the full story at BBC News Wales