Abstract: Nowhere is the conflict between economic progress and environmental quality more apparent than in the mineral extraction industries. The latter half of the 20th century saw major advances in the reclamation technologies. However, mine water pollution problems have not been addressed. In many cases, polluted mine water long outlives the life of the mining operation. As the true cost of long-term water treatment responsibilities has become apparent, interest has grown in the technologies that would decrease the production of contaminated water and make its treatment less costly. This is the first book to address the mine water issue head-on. The authors explain the complexities of mine water pollution by reviewing the hydrogeological context of its formation, and provide an up-to-date presentation of prevention and treatment technologies. The book will be a valuable reference for all professionals who encounter polluted mine water on a regular or occasional basis. Foreword; R. Fernández Rubio. Preface. 1. Mining and the Water Environment. 2. Mine Water Chemistry. 3. Mine Water Hydrology. 4. Active Treatment of Polluted Mine Waters. 5. Passive Treatment of Polluted Mine Waters

Abstract: The reclamation of former mining sites is a major challenge in many parts of the world. In relation to the restoration of spoil heaps (mine waste rock piles) and similar bodies of opencast backfill, key challenges include (i) the establishment of stable slopes and minimization of other geotechnical hazards (ii) developing and maintaining a healthy vegetative cover (iii) managing the hydrological behaviour of the restored ground. Significant advances have been made over the past four decades in relation to all four of these objectives. One of the most recalcitrant problems is the ongoing generation and release of acidic leachates, which typically emerge at the toes of (otherwise restored) spoil heaps in the form of springs and seepage areas. Such features are testament to the presence of a “perched” groundwater circulation system within the spoil, and their acidity reflects the continued penetration of oxygen to zones within the heaps which contain reactive pyrite (and other iron sulphide minerals). Two obvious strategies for dealing with this problem are disruption of the perched groundwater system and/or exclusion of oxygen entry. These strategies are now being pursued with considerable success where spoil is being reclaimed for the first time, by the installation of two types of physical barrier (dry covers and water covers). However, where a spoil heap has already been revegetated some decades ago, the destruction of an established sward or woodland in order to retro-fit a dry cover or water cover is rarely an attractive option for dealing with the “secondary dereliction” represented by ongoing toe seepages of acidic leachates. More attractive by far are passive treatment techniques, in which the polluted water is forced to flow through reactive media which serve to neutralize its acidity and remove toxic metals from solution. A brief historical review of the development of such systems reveals a general progression from using limestone as the key neutralizing agent, through a combined use of limestone and compost, to systems in which almost all of the neutralization is achieved by means of bacterial sulphate reduction in the saturated compost media of subsurface-flow bioreactors. In almost all cases, these passive treatment systems include an aerobic, surface flow wetland as the final “polishing” step in the treatment process. Such wetlands combine treatment functions (efficient removal of metals from the now-neutralized waters down to low residual concentrations, and re-oxygenating the water prior to discharge to receiving watercourses) with amenity value (attractive areas for recreational walking, bird-watching etc) and ecological value.