Managing our impacts through bioremediation

Water is one of the most valuable natural resources and is expected to become increasingly constrained over time. Safeguarding water sources through reduced consumption and quality stewardship is a priority globally as well as within the Mokhotlong region where our Letšeng operation is based.

Since Gem Diamonds started operating the Letšeng mine in 2006, the operation has prioritised the stewardship of water through a water management plan. The operational approach to water management has matured over time to align with appropriate best practice standards and operational trends in water use and impact. A comprehensive water monitoring protocol has been implemented at Letšeng, looking at both water quality on-site and downstream, as well as consumption volumes through mining and treatment activities.

In 2014, our Letšeng operation adopted a site-specific nitrate management plan. As part of this plan, the operation researched new water treatment technologies in collaboration with external subject matter experts. Working with the University of the Free State, bioremediation was identified as a priority technology for further assessment.  This led to the development of our bioremediation nitrate treatment solution, which was subjected to an intensive research and review process involving various experts both regionally and internationally.

Bioremediation is a strategy that uses naturally occurring micro- organisms to break down chemical compounds, such as nitrate, into less toxic substances, such as nitrogen gas (N2). The passive bioremediation method of remediation is especially appealing as it does not produce any toxic or hazardous waste products. Not only does bioremediation create significantly less waste than alternative treatment methods, such as reverse osmosis, but it is also more cost efficient and not as labour intensive.

At Letšeng, the bioremediation project is aimed at reducing blasting-related nitrate levels from water emanating from the mining operations’ facilities such as waste rock dumps and tailings storage facilities. During 2021, our bioremediation pilot plant was upgraded and re-commissioned to assess the denitrification efficiency of the improved technology. The pilot demonstrated the effectiveness of treating nitrates using naturally occurring micro-organisms.

A full-scale bioremediation plant is now being designed with construction to commence in 2022. This plant will treat water seeping from the waste rock dumps, historically the water source with the highest levels of nitrate. The treated water will then be discharged from this plant, into a newly constructed wetland to ensure sufficient water supply for downstream users.