The potential utilisation of indigenous South African grasses for acid mine drainage remediation

Abstract

Acid mine drainage (AMD) is a significant threat to the environment in South Africa and needs to be remedied. Although active treatment methods have been and are being implemented in industry, passive treatment systems involving bioremediation have the potential to be a more cost-effective and environmentally sustainable solution. Biological treatment of AMD involves the reduction of sulphate to sulphide by sulphate-reducing bacteria in the presence of a suitable organic substrate. This study tested the potential for indigenous grasses to be used as a carbon source in the bioremediation of AMD. Bioreactor experiments were conducted over a 70-day period to investigate whether indigenous grasses can be used to effectively reduce sulphate and iron concentrations, and increase the pH of an AMD solution. The results indicated that indigenous grasses hold promise for remediating AMD, as a maximum of 99% iron removal, 80% sulphate removal, and a final pH of 8.5 was achieved from initial conditions of 2 000 mg/ℓ iron, 6 000 mg/ℓ sulphate, and a pH of 3. Optimal results occurred in the bioreactor with Hyparrhenia hirta grass amended with soil containing microbes, although all bioreactors effected some form of remediation compared to the control.

Keywords: AMD, DSR, indigenous grass