ACID DRAINAGE FROM MINES AND ITS RELATED PROBLEMS - Prediction, quantification and implementation of mitigation measures are the key for enhancement of environmental standard
ACID DRAINAGE FROM MINES AND ITS RELATED PROBLEMS PREDICTION, QUANTIFICATION AND IMPLEMENTATION OF MITIGATION MEASURES ARE THE KEY FOR ENHANCEMENT OF ENVIRONMENTAL STANDARD
Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail: sharmapd1@gmail.com, Blogs/Websites: http://miningandblasting.wordpress.com/ , http://saferenvironment.wordpress.com Abstract Acid Mine Drainage (AMD), is the outflow of acidic water from mining operations including waste rock, tailings, and exposed surfaces in open pits and underground workings. ARD forms as a result of the dissolution of sulphides, mainly pyrite (FeS2) and pyrrhotite (FeS) under oxidizing conditions in air and water. This oxidation releases H+ ions and lowers the surrounding pH to acidic levels. Acidic drainage will subsequently leach additional metal ions from the adjacent rocks and deposit them. AMD is a problem because the vast majority of natural life is designed to live and survive at, or near, pH 7 (neutral). The drainage acidifies the local watercourses and so either kills or limits the growth of the river ecology. Mining operations lacking sufficient neutralizing carbonate minerals are at greatest risk of environmental degradation and usually require engineering intervention to minimize the problem. Although prevention of AMD is the most desirable option, a cost-effective prevention method is not yet available. The most effective method of control is to minimize penetration of air and water through the waste pile using a cover, either wet (water) or dry (soil), which is placed over the waste pile. Despite their high cost, these covers cannot always completely stop the oxidation process and generation of AMD. Application of more than one option might be required. Early diagnosis of the problem, identification of appropriate prevention/control measures and implementation of these methods to the site would reduce the potential risk of AMD generation. AMD prevention/control measures broadly include use of covers, control of the source, migration of AMD, and treatment.
INTRODUCTION Acid mine drainage (AMD) in general refers to the outflow of acidic water from metal mines or coal mines (including abandoned mines). AMD is one of the most perpetual pollution problems which occur world-wide in the mining areas. It refers to the distinctive type of wastewater that originates from the weathering and leaching of sulphide minerals present in coal and metal ore bodies. In fact, AMD from abandoned coal mines affects the quality of both groundwater and surface water. Drainage results from various mining methods performed in the watershed. These methods include underground mining, strip mining, and auger mining. The mining process exposes iron Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, 1 E.mail: sharmapd1@gmail.com, Blog: http://miningandblasting.wordpress.com/