Evaluation of Purification Efficiency of Passive Treatment Systems for Acid Mine Drainage and Characterization of Precipitates in Ilwal Coal Mine

Abstract

Artificial precipitation ponds, consisting of three steps of oxidation pond, successivealkalinity producing system (SAPS) and swamp, were constructed for the treatment of the acid mine drainagefrom the Iwal coal mine. The efficacies of the passive treatment system in terms of neutralization of minewater and removal of dissolved ions were evaluated by the chemical analyses of the water samples. Minewater in the mine adits was acidic, showing the pH value of 2.28-2.42 but the value increased rapidly to6.17-6.53 in the Oxidation pond. The purification efficiencies for the removal of Al and Fe were 100%,whereas those of SO4, Mg, Ca, and Mn were relatively low of 50%, 40%, 24%, and 59%, respectively. Theseresults indicate a need for application of additional remediation techniques in the passive treatment systems. The precipitates that formed at the bottom of the mine water channels were mainly schwertmannite(Fe8O8(OH)6SO4) and those in the leachate water were 2-line ferrihydrite (Fe2O30.5H2O).