With water scarcity and quality being fundamental risks to South Africa’s mines, necessitating that operations understand and develop water management strategies that ensure their viability, the comprehensive strategy of a North West platinum mine presents a level of management to aspire to, posits mining industry consultant The MSA Group principal environmental consultant Robin Bolton.
tells Mining Weekly that the North West operation (which cannot be named for contractual reasons) recently developed a water management strategy, inclusive of a three-year implementation plan and water efficiency targets.
The operation undertook this strategy to counter shortfallings in its water management, namely the remediation of a significant amount of nitrate-contaminated groundwater, pollution control dams incorrectly operating at full capacity, the inefficient use of municipal water where scope exists for recycling water and the reduction of related costs. Further, it also partially fulfilled its safety, health and environmental, sustainability and climate change corporate policies through this undertaking.
Bolton indicates that the process of determining efficiency targets was predicated on ascertaining baseline water use, with a sustainable 10% reduction in yearly water consumption agreed on. This reduction, in conjunction with a planned increase of production, is expected to yield cost savings of more than R4-million.
This strategy involved the investigation of different scenarios to determine the most efficient solution/s for the recycling of water and the remediation of contaminated water using the strategy’s updated water balance and groundwater models, he notes.
One scenario involved the lining of all storage dams to mitigate the contamination of groundwater, especially in backfilled areas, as well as the construction of an appropriate silt trap to reduce the amount of sediment entering the dams, thereby reducing its storage capacity and the subsequent cleaning required.
Another scenario entailed using deeper cutoff trenches around the tailings storage area to intercept and capture contaminated groundwater, thus preventing the expansion of the plume and seepage into the deeper aquifer. A third scenario entailed using scavenger wells to abstract nitrate-contaminated water. The water from these two options would be used as ‘makeup’ for certain processes where possible, thus a dual benefit would result through containing and remediating groundwater and recycling water.
A fourth scenario entailed upgrading the underflow specific gravity (SG) management to improve its efficiency, says Bolton, explaining that an error on the SG measurement of as little as 5% can have repercussions on the water reclamation potential of over 100 m3.
It is vital that mines manage water correctly to accommodate for the water-intensive nature of mining and the reliance on a substantial quantity of water for almost every stage of the process.
The water management imperative is affected by many factors, including climate change, increasing water costs, security of water supply and the water needs of surrounding communities. Further, a growing awareness of mine water management by investors and surrounding communities has been registered by mines, with Bolton stating that this is further compounded by many mines, especially those in the southern hemisphere, being located in water-stressed areas.
Water management is, therefore, integral in identifying a sufficient, sustainable water resource for use in mine processes. Bolton indicates that this entails ascertaining and investigating all possible water sources, inclusive of surface water, groundwater, rainwater and any third-party supplier of water such as neighbouring operations or municipalities.
Moreover, he stresses that there are several vital factors that must be reviewed when investigating the feasibility of these options – the cost and size of infrastructure, such as dams, pipelines and flowmeters, as well as buying water from a supplier.
Weather, specifically rainfall, is another factor, with patterns, frequency and intensity to be tracked, explains Bolton, adding that recourse to reducing the loss of evaporation, for example, by storing water underground, should also be considered.
Further, licensing requirements need consideration, specifically with regard to the time needed to obtain a water use licence and the possible risk involved if this licence is not secured. The management of storm water, the reduction of water contamination and water treatment options are also factors.
Regarding users’ reliance on groundwater, the availability of potable water, sanitation standards and their water-quality expectations must be considered by mining companies as elements to accommodate.
Bolton avers that the mining industry is aware of and has been successfully using a number of water conservation initiatives and strategies. However, i
n Bolton’s experience, the water balance, which is fundamental to understanding operations’ water uses and opportunities for savings, is generally inaccurate or out of date. He also notes inadequate water-quality monitoring, outdated groundwater models, nonexistant or outdated stormwater plans and water leaks as common water use inefficiencies, as well as highlights information gaps on mines.