Good quality water is a critical resource essential for human, animal and plant survival. However, globally, human activities both domestic and industrial continue to pose serious threat to the availability of quality water needed to meet growing demand especially in a period where climate change impact has worsened and the drive towards zero carbon emissions has also intensified. There is an urgent need for businesses especially those in the extractive sector to adopt and utilize advanced mineral technologies that enhance sustainable water management practices such as enabling water to be recycled and re-used to reduce water consumption and pollution.
This article briefly discusses how mining activities impact water resources; and secondly looks at how the ‘Gold Kacha’ mercury-free mineral processing technology for small scale gold mining contributes in reducing water consumption and pollution in Ghana.
How mining impact water resources
Mining is one of the major human and industrial activities that have critical impact on the availability and quality of water. Mining operations often consume significant amounts of water for various processes, including mineral extraction, dust suppression, equipment cooling, and employee facilities. According to a recent report1 by the Energy Transmission Commission, mining metals consumes about 4 billion m3 of water annually, half of what is consumed by coal mining. It further estimated that by 2050, water consumption in mining metals for the energy transition could reach 4.5 billion m3.
Chart Source: Energy Transition Commission (2023)
Although the consumption of freshwater in mining accounts for only a small proportion of the total water use at global and even national scales, excessive water usage by mining operations can strain local water resources, especially in water-scarce regions. It is reported that in some regions in Australia and South America, mining water consumption exceeds the natural water availability for a regional river basin2. Diverting large amounts of water for mining purposes can reduce the availability of water for other uses, such as agriculture, drinking water, and ecosystem support.
Mining activities can also release various pollutants into water bodies, including heavy metals, acids, and chemicals used in the extraction and processing of minerals. These pollutants can contaminate surface water and groundwater, posing risks to aquatic life, wildlife, and human health. Contaminated water from mining activities can pose health risks to nearby communities that rely on water sources for drinking, bathing, and irrigation. Elevated levels of pollutants can disrupt food chains and reduce biodiversity.
Open-pit and underground mining can disrupt natural groundwater flow patterns, leading to the depletion of groundwater reserves. This can affect the availability of water for communities and ecosystems that rely on groundwater. Mining activities can also disturb soil and vegetation, leading to increased erosion and sedimentation in nearby water bodies. Sediments can clog waterways, degrade water quality, and harm aquatic habitats. Mining can alter natural drainage patterns and water flow regimes, affecting downstream water bodies and habitats.
When sulfide minerals are exposed to air and water during mining, they can oxidize and produce acidic runoff. This acidic drainage can leach heavy metals and other contaminants from the surrounding rocks, leading to the contamination of water bodies.
The storage and disposal of tailings (waste materials from mining) also pose a significant water-related risk. Poorly managed tailings facilities can result in tailings dam failures, which may lead to the release of large volumes of contaminated water into the environment.
The ‘Gold Kacha’ intervention in reducing water consumption and pollution
The availability of quality water for human and agricultural usage in Ghana is seriously under threat due to the alarming rate of water pollution occasioned by the incessant illegal mining activities and poor mining waste disposal. Several studies and reports have revealed high concentration of heavy metals such as mercury, lead, and arsenic in river bodies such as Pra, Ankobra, Densu, Tano and several others, as a result gold mining operations mostly by illegal miners as well as poor disposal of tailings by some artisanal and small scale miners3,4. This has led to various kinds of chronic health problems such as neurological damage, kidney problems, memory loss, miscarriages, arthritis, psychotic reactions, and even death in mining communities.
The ‘Gold Kacha’ is a mercury-free technology introduced to boost the operations of small scale miners with over 90% gold recovery and also to minimize the negative environmental impact that characterizes the small scale mining sector. It is part of the full modular mercury-free mineral processing technology (from ore-crushing to smelting) supplied by Commodity Monitor Limited in Ghana for small scale mining.
The ‘Gold Kacha’ is a centrifugal concentrator with novel centrifugal riffle principle which enables high recovery of both coarse and fine precious metals without the use of mercury or any chemical. It is also able to remediate mercury from contaminated tailings which enable the mercury that would have polluted the environment to be safely discarded.
The ‘Gold Kacha’ in operation
The Gold Kacha is designed to enable small scale miners use relatively low quantity of water in gold extraction and also prevent water pollution since it cannot be mounted on water bodies. With a feed rate of 3 tonnes per hour, the Gold Kacha uses at maximum 4m3 of water per hour. The Kacha is designed to work effectively with the 3-pond water purification and recirculation model.
With the 3-pond system, fresh water is pumped into the third pond which is used to process gold ore through the Gold Kacha. The Kacha comes with a sluice through which the tailings are discharged to the first pond. Solid materials from the tailings settle in the first pond and water overflows with time into the second pond where finer particles settle. Water with a lower load of suspended solids overflows into the third pond which is pumped for re-use to process gold ore reducing the need for fresh water intake. With time, the third pond can be emptied and water (without any mining effluent) safely disposed to allow for the pond to be refilled with fresh water.
This system enables the same quantity of water to be used for processing gold ore for several days hence reducing water consumption and cost. It also enables miners to monitor the amount of water used in their operations. Moreover, the system does not allow the discharge of tailings directly into water bodies and coupled with the non-usage of mercury in gold processing, there is no pollution of water bodies.
Full set-up of Mercury-free mineral processing plant on a 3-pond system at a small scale mining site
This means that miners who adopt this mineral processing technology would significantly decrease water consumption and cost in their operations as well as lessen pollution of local water bodies thereby reducing water stress and demand on local water supply. The ‘Gold Kacha’ technology therefore has a great potential to reverse the damages created by artisanal and small scale mining activities on water bodies in mining communities. Reducing water consumption and pollution in mining is essential for conserving this valuable resource and minimizing environmental impacts.
References:
- Energy Transition Commission (2023). Material and Resource Requirements for the Energy Transition.
- Meissner, S. (2021). The impact of metal mining on global water stress and regional carryingcapacities – A GIS-Based Water Impact Assessment. Resources 10 (120), 1-34.
- Ofosu, G., & Sarpong, D. (2022). Beyond the doom: Sustainable water management practices of small-scale mining operations. Resources Policy, 77, 1-8.
- Anang et al., (2023). Mercury and lead pollution in rivers in Ghana: geo-accumulation index, contamination factor, and water quality index. Water Practice & Technology 18(5), 1273-1283.
