Organic substrates as electron donors in permeable reactive barriers for removal of heavy metals from acid mine drainage

Abstract

This research was conducted to select suitable natural organic substrates as potential carbon sources for use as electron donors for biological sulphate reduction in a permeable reactive barrier (PRB). A number of organic substrates were assessed through batch and continuous column experiments under anaerobic conditions with acid mine drainage (AMD) obtained from an abandoned lignite coal mine. To keep the heavy metal concentration at a constant level, the AMD was supplemented with heavy metals whenever necessary. Under anaerobic conditions, sulphate-reducing bacteria (SRB) converted sulphate into sulphide using the organic substrates as electron donors. The sulphide that was generated precipitated heavy metals as metal sulphides. Organic substrates, which yielded the highest sulphate reduction in batch tests, were selected for continuous column experiments which lasted over 200 days. A mixture of pig-farm wastewater treatment sludge, rice husk and coconut husk chips yielded the best heavy metal (Fe, Cu, Zn and Mn) removal efficiencies of over 90%.

Keywords:

• acid mine drainage
• permeable reactive barrier
• mixed organic substrate
• heavy metal removal
• sulphate reducing bacteria

Acknowledgements

This research was supported through the UNESCO-IHE Partnership Research Fund (UPaRF), The Netherlands under the project ‘Permeable Reactive Barrier for Remediation of Acid Mine Drainage (60042391 UPaRF PRBRAMD Type III)’, the ‘Industrial & Hazardous Waste Treatment & Management’ project under the Asian Regional Research Programme on Environmental Technology (ARRPET) funded by the Swedish International Development Cooperation Agency (Sida), and the Erasmus Mundus Joint Doctorate Programme on Environmental Technologies for Contaminated Solids, Soils, and Sediments () (FPA no. 2010-0009).