Tropical Futures: Mineral Program and BNA

Managing acid mine drainage in northern Australia using microbial mats

David Parry, Karen Gibb, Brett Neilan, Claire Streten-Joyce, Judy Manning

Project summary

The metal rich acidic discharge from acid mine drainage can lead to significant environmental damage (Figure 1 and 2). Acid mine drainage is a serious issue in northern Australia and current acid mine drainage treatment technologies are not successful because of extreme seasonal changes. Microbial treatment technologies such as mats and bioreactors may be suitable for the tropics and these approaches are more likely to be successful if they use local, well adapted microbes. With our industry partners will identify candidate microbes and trial mat treatments for acid mine drainage and neutral drainage. Such treatments will be applicable in the tropics at a global level.

What is acid mine drainage?

Acid mine drainage can be a natural process, occurring through exposure of sulfidic minerals to atmospheric conditions and leading to the production of sulfuric acid. In mining, however, the process can be accelerated and microbes contribute to acid formation through the regeneration of iron, which is the primary oxidant of pyrite. Sulfate reducing bacteria oxidise organic compounds and produce hydrogen sulfide and bicarbonate ions and this reduces the acidity. The sulfide reacts with metals to form insoluble metal sulfides that precipitate out of solution. As a result of this buffering and metal precipitation there is interest in the use of engineered anaerobic sulfate reducing bacteria reactors to remove heavy metals.

Figure 1. East Branch of the Finniss River, Northern Territory looking towards Rum Jungle, a legacy uranium/copper mine site leaching acid. The white material on the left hand bank are evaporites from the acid mine drainage, the cobbles in the creek are algal mats and the pH is around 3.8. Photo courtesy Jenny Brazier, Charles Darwin University and Environmental Research Institute of the Supervising Scientist (eriss) - Darwin Office.

 

Figure 2. Evaporites (salts containing a range of metals) resulting from acid mine drainage from the Rum Jungle mine site, Northern Territory. Photo courtesy of Jenny Brazier, Charles Darwin University and eriss.

 

 

 

Industry partners:

• Compass Resources: www.compassnl.com.au
• Northern Territory Government: www.nt.gov.au/dpifm
• Vista Gold Corp: www.vistagold.com
• Xstrata Zinc - McArthur River Mining: www.mcarthurriver.com.au
• Zinifex Century Mine: www.zinifex.com

Related links:

• Bioscience North Australia: www.cdu.edu.au/ehs/bna
• Environmental and Analytical Chemistry Unit: www.cdu.edu.au/ehs/science/EACU/index.html
• University of New South Wales: www.babs.unsw.edu.au/research/ehm/index_ehm.html
• International Network on Acid Prevention: www.inap.com.au

Additional reading:

• Baker & Banfield 2003 FEMS Microbiol. Ecol. 44:139-52
• Bender et al. 1995 J. of Industrial Microbiol. 14:113-18
• Bender & Phillips 2004 Bioresour. Technol. 94:229-38
• Harries 1997 Supervising Scientist report 125, Aus. Gov. Dep. Environ. Heritage
• Jong & Parry 2003 Water Res. 37:3379-89
• Jong & Parry 2005 Chemosphere 60:254-65
• Taylor et al. 2005 A summary of passive and active treatment technologies for acid and metalliferous drainage. in 5th  Australian Workshop on acid drainage
• Tsang & Parry 2004 Aust. J. Chem. 57:96-100