MANAGEMENT OF ACID MINE DRAINAGE (AMD) IN INDIAN COAL MINES Proceedings of the XI International Seminar on Mineral Processing Technology (MPT-2010) Editors: R. Singh, A. Das, P.K. Banerjee, K.K. Bhattacharyya and N.G. Goswami © NML Jamshedpur, pp. 1163–1170 MANAGEMENT OF ACID MINE DRAINAGE (AMD) IN INDIAN COAL MINES B.P. Baruah, Puja Khare and P.G. Rao Coal Chemistry Division, North-East Institute of Science & Technology (CSIR-NEIST), Jorhat - 785006, Assam ABSTRACT Mining practices, present and past, contribute towards environmental degradation affecting the ecosystems and human health. The unscientific coal mining in the tertiary North Eastern Region (NER) Indian coal mines poses a serious threat to the environment. Dumping of waste rocks including mine rejects generated during mining adds to the problem by aqueous weathering and discharge of acidic effluents. The coal mining in Meghalaya causes large-scale destruction and degradation of the environment. Coal extraction in the state is done by primitive sub-surface mining methods commonly known as ‘rat hole’ mining. The indiscriminate and unscientific mining, absence of post mining treatment and management of mined areas are making the fragile ecosystems more vulnerable to environmental degradation and leading to land use changes. The main problems in Meghalaya are the production of Acid Mine Drainage (AMD) in nearby areas by continuous leaching of acidic waste from the coal mining sectors. An Environmental Management Plan (EMP), has been developed for management of AMD in high sulphur coalmines by simulation of AMD from weathered coals and mine rejects. Sequential alkalinity producing (SAP) coupled with biological processes found effective in controlling AMD and reducing TDS, Conductivity, SO 4 and toxic elements. In this paper, the state of art for AMD and the processes suitable for the management of AMD are discussed. Keywords: AMD, EMP, Acid generating processes, State of Art for AMD. INTRODUCTION Coal and metal mining disturb large volumes of geological materials and are exposed to the environment. The exposure to air and water, the sulfide minerals commonly associated with coals and metal deposits are oxidized and hydrolyzed resulting in Acid Mine Drainage (AMD) formation. AMD is a low pH, sulphate rich water with high amounts of acidity. The acidity is comprised of mineral acidity (Fe, Al, Mn and other metals depending upon the geological deposit) and also hydrogen ion concentrations. The pyrites present in coal and overburden (OB) materials are leached to form low pH drainage water originating largely due to metabolic activity of Thiobacillus ferooxidans. These microbes are acidophillic and capable of surviving in low pH and catalyze the pyrite oxidation. It obtains its energy by the oxidation of either iron or sulphur. Chemical or biological pyrite oxidation by molecular oxygen or Fe (III) ions is described by the following reactions: 1163 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by eprints@NML