Mine Water Treatment with a Pilot Scale RAPS-System
In 1985, economic reasons caused the closure of the fluorspar mine “Hohe Warte” near Gernrode in the German Harz Mountains. Though remediation works were conducted in the preceding years, mine water is currently flowing out freely of the dewatering adit and is impacting the environment and the receiving brook. The mine water is characterised by low pH-values, high conductivities and contains considerable amounts of iron, manganese, and arsenic. Annually, the mine discharges 0.7 Mio m of mine water with 7.8 tons of iron, 3.8 tons of manganese and 13 kg of arsenic. Therefore, the discharging mine water has a great potential to affect the quality of the receiving streams and resulted in a decrease of biological diversity. Based on hydrogeological and hydrochemical investigations, a passive treatment system would be able to treat the mine water. In February 2003 a pilot system was installed near the dewatering adit consisting of a settlement pond, a RAPS system and a constructed wetland. It could be shown that this passive system was able to treat an aliquot of the mine water down to ecologically acceptable standards.
Deep mine hydrogeology after closure: insights from the UK
Although the UK has had an extremely rich history of deep mining, at the start of the 21st Century most mines are already abandoned and in various stages of flooding. Lessons of generic value have been obtained in the UK over the last decade, particularly in relation to the reactivation of mine subsidence processes during flooding of old workings, and the generation and release of polluted drainage. As researchers and practitioners have attempted to characterise and (in some cases) predictively model such processes, new analytical techniques have been developed. These range from simple ’rules of thumb’ for pollution intensity prediction to sophisticated 3-D models of flow through networks of mine roadways routed through variably-saturated porous media.
Holistic remedial strategies for short- and long-term water pollution from abandoned mines
Abstract Where mining proceeds below the water-table—as it has extensively in Britain and elsewhere—water ingress is not only a hindrance during mineral extraction but also a potential liability after abandonment. This is because the cessation of dewatering that commonly follows mine closure leads to a rise in the water-table and associated, often rapid, changes in the chemical regime of the subsurface. Studies over the past two decades have provided insights into the nature and time-scales of these changes and provide a basis for rational planning of mine-water management during and after mine abandonment. The same insights into mine-water chemistry provide hints for the efficient remediation of pollution (typically due to Fe, Mn and Al and, in some cases, Zn, Cd, Pb and other metals). Intensive treatment (by chemical dosing with enhanced sedimentation or alternative processes, such as sulphidization or reverse osmosis) is often necessary only during the first few years following complete flooding of mine voids. Passive treatment (by the use of gravity-flow geochemical reactors and wetlands) may be both more cost-effective and ecologically more responsible in the long term. By the end of 1999 a total of 28 passive systems had been installed at United Kingdom mine sites, including examples of system types currently unique to the United Kingdom. Early performance data for all the systems are summarized and shown to demonstrate the efficacy of passive treatment when appropriately applied.