Managing the potential risks of using bacteria-laden water in mineral processing to protect freshwater.

The minerals industry is being driven to access multiple water sources and increase water reuse to minimize freshwater withdrawal. Bacteria-laden water, such as treated effluent, has been increasingly used as an alternative to freshwater for mineral processing, in particular flotation, where conditions are favorable for bacterial growth. However, the risk posed by bacteria to flotation efficiency is poorly understood. This could be a barrier to the ongoing use of this water source. This study tested the potential of a previously published risk-based approach as a management tool to both assist mine sites in quantifying the risk from bacteria, and finding system-wide cost-effective solutions for risk mitigation. The result shows that the solution of adjusting the flotation chemical regime could only partly control the risk. The second solution of using tailings as an absorbent was shown to be effective in the laboratory in reducing bacterial concentration and thus removing the threat to flotation recovery. The best solution is likely to combine internal and external approaches, that is, inside and outside processing plants. Findings in this study contribute possible methods applicable to managing the risk from water-borne bacteria to plant operations that choose to use bacteria-containing water, when attempting to minimize freshwater use, and avoiding the undesirable consequences of increasing its use.

Quantitative risk-based approach for improving water quality management in mining.

The potential environmental threats posed by freshwater withdrawal and mine water discharge are some of the main drivers for the mining industry to improve water management. The use of multiple sources of water supply and introducing water reuse into the mine site water system have been part of the operating philosophies employed by the mining industry to realize these improvements. However, a barrier to implementation of such good water management practices is concomitant water quality variation and the resulting impacts on the efficiency of mineral separation processes, and an increased environmental consequence of noncompliant discharge events. There is an increasing appreciation that conservative water management practices, production efficiency, and environmental consequences are intimately linked through the site water system. It is therefore essential to consider water management decisions and their impacts as an integrated system as opposed to dealing with each impact separately. This paper proposes an approach that could assist mine sites to manage water quality issues in a systematic manner at the system level. This approach can quantitatively forecast the risk related with water quality and evaluate the effectiveness of management strategies in mitigating the risk by quantifying implications for production and hence economic viability.

Mining drives extensive deforestation in the Brazilian Amazon.

Mining poses significant and potentially underestimated risks to tropical forests worldwide. In Brazil's Amazon, mining drives deforestation far beyond operational lease boundaries, yet the full extent of these impacts is unknown and thus neglected in environmental licensing. Here we quantify mining-induced deforestation and investigate the aspects of mining operations, which most likely contribute. We find mining significantly increased Amazon forest loss up to 70 km beyond mining lease boundaries, causing 11,670 km2 of deforestation between 2005 and 2015. This extent represents 9% of all Amazon forest loss during this time and 12 times more deforestation than occurred within mining leases alone. Pathways leading to such impacts include mining infrastructure establishment, urban expansion to support a growing workforce, and development of mineral commodity supply chains. Mining-induced deforestation is not unique to Brazil; to mitigate adverse impacts of mining and conserve tropical forests globally, environmental assessments and licensing must considered both on- and off-lease sources of deforestation.