Efficacy of Limestone and Laterite Mine Waste in the Passive Treatment of Acid Mine Drainage

Abstract

Acid mine drainage (AMD) treatment is continuously being researched due to its detrimental effects to the surrounding ecosystem and nearby communities. Although active treatment is the most widely used approach, the system needs constant input which does not make it viable in the long term. Since AMD persists long after abandonment of mine operations, passive treatment system may provide the long-term solution that can be made sustainable using materials that are cheap and derived from waste. Laterite mine waste (LMW) has shown its potential as an effective treatment media for heavy metals in AMD. In this study, the efficacy of this material to complement the performance of limestone was examined at four different ratios. The materials were placed in a layered setup to allow each material to be independent of the breakthrough point of the other. Water quality parameters (pH and conductivity) were measured along with Cu, Fe, and Ni. The results showed that a longer residence time and an increasing amount of LMW yielded better effluent quality in general. At the 30-min mark, the 25:75 (w/w) ratio of limestone and LMW increased pH from 2.24 to 5.84 while achieving a 99 % reduction for Cu, 93 % for Fe, and 63 % for Ni.