MERG (Mining Environment Research Group) and Viceroy's Brewery Creek Mine commissioned a study by Microbial Technologies Inc., to determine the viability of biological detoxification of spent heaps in Northern (Arctic) environments. This approach has been applied at a small number of mine sites in North America, but it remains a relatively unproven technology. In particular, the detoxifying ability of microorganisms indigenous to Northern mine sites remained to be demonstrated. This approach may be advantageous for the Yukon Territory because it relies on bacteria grown on site to destroy cyanide, as compared with importing (potentially large quantities) of hydrogen peroxide.
The study was designed to answer two questions::
1) Is biological detoxification a feasible option for Brewery Creek Mine?
2) Is this process likely to be applicable to other similar operations in the Yukon Territory and other Northern locations?
There is virtually no information on the abundance and distribution of bacteria capable of degrading cyanide in the Arctic. It is known that different bacterial species degrade different metal-cyanide complexes, such as iron-cyanide or nickel-cyanide complexes. Thus, it is important to determine both the abundance and the metabolic diversity of micro-organisms metabolizing metal-cyanide complexes. The first phase of the study involved collecting, enumerating, and culturing such micro-organisms from the mine sites.
Cyanide-degrading bacteria may be present in the mine environment, but they may not be able to detoxify the ore from the spent heap. For example, they may be incapable of colonizing the ore or they may be inhibited by high cyanide concentrations or some toxicant in the ore (e.g., arsenic, mercury). Phase 2 of the study was a column study to determine if bacteria collected and grown in Phase 1 can detoxify spent ore collected from Brewery Creek's heap. Their ability to destroy cyanide was compared with that of hydrogen peroxide, the conventional chemical treatment of spent heaps.
