The Aster process is an aerobic, micro-biological thiocyanate and cyanide treatment process, which enables gold producer Nordgold’s Suzdal plant, located in Kazakhstan, to achieve a number of effici-ency enhancements, while adhering to its environmental protocols, says Suzdal plant operations manager Dr Olga Tupikina.

One of the key benefits afforded by the process is that it enables the plant to recycle water through the purification process for the bioleaching of sulphide minerals, removing the risk of the water supply becoming frozen during winter and ensuring stable gold produc-tion year round.

“It was important for us to secure our supply of water, especially in winter, when there is often a shortage. However, thiocyanate and cyanide are toxic to biological oxidation microbes, requiring us to clean the water of these compounds before recirculating it,” says Tupikina.

Further, the water treatment system also enables the reuse of water in the plant’s tailings dam, rendering the construction of a new dam unnecessary and helping to reduce additional capital costs.

“We investigated other technologies, such as the electrochemical treatment of the water, but this was not as efficient. After conducting a comprehensive series of tests using various other technologies, we settled on the Aster process as the most effective solution,” says Tupikina.

Kazakhstan has a rich history of mining and it boasts a highly skilled industry workforce. The Suzdal operation also has considerable expertise in its metallurgical laboratory, with engineers who have significant experience in biological oxidation and microbiological processing. This has enabled the smooth imple-mentation of the Aster process at the plant.

“Incorporating another bacterial technology into our plant was not difficult as our employees have significant experience in operating biological oxidation processes,” adds Tupikina.

The process is also in line with Nordgold’s strict environmental policies.

“Our environmental regulations require that we do not discharge water into the environ-ment. Adopting the Aster process means we can now treat our tailings water to use as process water, which is an ideal fit for our operation,” says Tupikina.

The organisms are fed using molasses, which can be sourced in abundance locally, ensuring a secure supply.

Biological processing company Biomin provides the Aster treatment process. It installed a pilot plant at Suzdal to conduct tests prior to constructing a full-scale process.

“The Aster treatment process allows com- panies to be efficient with their capital expendi-ture while also providing an effective solution to meet their environmental commitments,” adds Biomin process manager Craig van Buuren.

Since implementing the Aster process, Suzdal reports significant adaptation to local conditions by the microorganisms. Its work-force’s experience in operating microbiological processes means that plant engineers have the expertise to manage the introduction of local microorganisms into the process in a way that enhances the overall result.

“That the process organisms are adapting so well to the site’s conditions and working in synergy with the local organisms is evidence of the success of our management of the Aster process and the flexibility it has as a treatment solution. It has enabled us to increase efficiency in an environmentally responsible way – a goal that remains at the heart of Nordgold’s policy,” concludes Tupikina.