COMPARATIVE EVALUATION OF TREATMENT TECHNOLOGIES FOR ACID MINE DRAINAGE

摘要

Acid Mine Drainage (AMD) is one of the most difficult problems to address. Acid Mine Drainage is characterized by low pH, elevated heavy metals, sulfate, and total dissolved solids (TDS). Once acid mine drainage is released into the streams, the heavy metals can be transported considerable distance downstream. However, several physical and chemical processes operating in a stream can give rise, directly or indirectly, to attenuation of pollutants. Metals released by the acid mine drainage are hydrolyzed when the pH increases due to dilution by receiving streams, resulting in precipitation of metals on the stream substrate. While precipitated metals adsorbed to sediment particles are carried downstream, potentially contributing to bioaccumulation by aquatic organisms, the dissolved and hydrolyzed metals in the process of forming precipitates cause acute toxicity downstream of the confluence of the acidic tributary. Also, with the precipitation of Iron hydroxide, known as yellow boy, the aesthetics of the stream are also destroyed. Traditional treatment technologies find limited applicability in the treatment of acid mine drainage because of the wide spatial distribution of the source, and hence it demands for alternate treatment technologies. The various technologies that are available for the treatment of acid mine drainage can be subdivided into two major categories - active treatment methods, namely chemical treatment and passive treatment methods, namely aerobic wetlands, compost or anaerobic wetlands, bioleaching, diversion wells, open limestone channels, anoxic limestone drains, and vertical flow reactors. This paper comparatively evaluates the applicability of the treatment technologies for various aqueous composition of acid mine drainage. Based on this a tool has been developed for selecting the best treatment method for an acid mine drainage producing mine.