How can contaminated water from coal mines be treated in confined sites?
The challenge
Many of South Wales’ former mining areas continue to suffer from impoverished rivers due to mine water pollution. The high levels of iron and other metals are potentially damaging to the health and landscape of these communities.
Existing treatment methods such as settling ponds and reed beds can be highly effective, but are often not feasible since they require large areas of land. For mines where such space is not available, the Coal Authority needed a technique that would provide the same effective treatment, but with a much smaller footprint.
The solution
Researchers at Cardiff University worked alongside experts from the Coal Authority at former UK coalmines, including the former Taff Merthyr colliery in the heart of the South Wales coalfield. They discovered that the ochre sludge that precipitates from the mine waters was not just part of the problem but could potentially become part of the treatment solution.
When mine water comes in contact with the ochre sludge it actually speeds up the process of iron and manganese removal. It was the discovery of this ‘autocatalysis’ process that enabled the development of a new system that enabled mine water to be treated in a much smaller area. The novel Vertical Flow Reactor (VFR) developed in the project led to new engineering guidelines for their design.
Furthermore, on going work between Cardiff University and the Coal Authority has demonstrated the application of carbon dioxide stripping technology for mine water treatment, and led to improved understanding of treatment process for improved design of conventional and non-conventional mine water treatment systems for industry.
Resulting benefits
The Cardiff VFR technology will enable the Coal Authority to treat mine water at sites where this was not previously feasible, and achieve significant cost savings.
Dr Ian Watson from The Coal Authority said: "The Coal Authority is responsible for environmental protection related to abandoned coal mines – specifically the treatment of mine water pollution. Working alongside experts from Cardiff University we have been able to gain a greater understanding and create new mine water treatment technologies, which improves water quality and promotes public safety in these areas."
Future directions
It is anticipated that the work between Cardiff University and the Coal Authority can be rolled-out across other former mining sites across the UK, with knowledge also being transferred more widely, for example to civil engineering firms. The technology is also applicable internationally.
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