Abstract:

Acid mine drainage (AMD) generated through the oxidation of pyrite facilitated by Acidithiobacillus ferrooxidans has a lower pH and contains relatively high contents of heavy metals as well as Fe and SO2-4. Iron oxyhydrosulfate and iron oxyhydroxide, commonly found in acid mine drainage (AMD) and in waters polluted by AMD, play important roles in the attenuation or scavenging of toxic elements. These ferric iron precipitates include jarosite, schwertmannite, goethite, ferrihydrite, etc. In the light of the formation process of biogenic ferric iron oxyhydrosulfate in AMD and its role in scavenging of Fe, SO2-4 and toxic metals, the biogenic minerals could be considered an effective adsorbent for arsenic removal of Ascontaminated groundwater because biogenic ferric iron oxyhydrosulfate especially schwertmannite is of extreme high adsorption capacity for As(III) up to 120 mg/g. For enforced AMD treatment, the ferrous iron biooxidation and ferric iron oxyhydrosulfate formation process by Acidithiobacillus ferrooxidans could be introduced into a conventional lime neutralization active treatment system to form a twostep treatment approach including enforced biooxidation and biogenic minerals formationlime neutralization, which will reduce drastically the amount of lime needed and improve the separation of precipitate and the purification of water. In addition, Acidithiobacillus ferrooxidansloaded biological permeable reaction barrier (bioPRB), in which ferrous iron oxidation and secondary biogenic minerals formation will be able to occur, is designed and applied to AMD passive treatment system with limestone drains to constitute a new treatment model. This can increase the longevity of limestone drains in treating acid mine drainage containing high concentrations of iron and heavy metal. Among others, the advantages of secondary biogenic mineras formation applied in the treatment for AMD or Ascontanminated groundwater are also discussed. Furthermore, the future research topics are proposed.

Key words:

Acidithiobacillus ferrooxidans; acid mine drainage; iron oxyhydrosulfate; arsenic; underground water; lime neutralization