The contamination of natural systems by mining activities, which can generate large volumes of chemically hazardous waste, has the potential to negatively impact environmental and human health. The wide diversity of potentially useful microbial metabolic pathways, allows for the effective treatment of a variety of such waste streams. This talk will detail a project focused on the design and implementation of a biological treatment for thiocyanate (SCN-) contaminated waste at a gold mine in Victoria. SCN- is a stable by-product of the use of cyanide in the gold extraction process, found at high concentrations in gold mine wastewater and associated contaminated waters. The treatment of SCN- contaminated water is challenging using conventional chemical oxidation, however, a number of bacteria have been found to be capable of SCN- biodegradation, using it as an energy, sulfur, nitrogen and/or carbon source.
In order to address the various pools of SCN-, found in process, ground and surface water at the mine in Victoria, both promoted natural attenuation (in situ) and engineered (ex situ) approaches have been investigated. Through lab and field studies, SCN- degradation by the extant microbial community was successfully promoted, in situ in the surface storage water. This work was able to reveal details on the complex microbial community dynamics during in situ SCN- degradation and subsequent cycling of its sulfur, carbon and nitrogen products. Parallel to this work, the development of an engineered bioreactor solution, able to treat both new process water and contaminated legacy water, was trialled. Lab studies enabled probing of the genetic and metabolic diversity of this system and revealed the impact of environmental controls on SCN- degradation and nutrient cycling. These studies have helped inform the design and construction of a pilot scale SCN- degrading bioreactor series at the mine site. Overall this project serves as an example of how the metabolic capability of microbial communities can be effectively applied to challenging environmental problems.