Mine managers are investigating the use of existing wetlands or creating wetlands to passively treat some of their used water, thereby reducing the volume of water that needs to be actively treated before and during discharge, says multidisciplinary engineering consulting firm WSP Africa environment and energy senior associate Karen King.
Moreover, conjunctive planning is increasingly undertaken, whereby mine managers use a combination of surface water and groundwater resources in a specific plan depending on the season and the climatic conditions.
“There are many ways to save water,” King asserts, noting that WSP is working on a study centred on passive water treatment at a colliery, where the water is diverted directly from a wetland system at a very deliberate rate to the water treatment system.
King notes that, while the consideration of wetlands for passive water treatment is evident in the coal mining industry, this treatment option is not limited to a specific mining sector.
Further, existing wetlands are functioning systems, which can provide the existing coarse and fines materials, as well as bugs to assist in water treatment.
King, however, emphasises that the water has to be of a certain quality to enable the system to handle the amount and quality of the water. Residence time is also key in enabling the system to clean the water.
King notes that the type of solutions used to treat mine water depend largely on the volume and quality of the water, as well as the size of the operation.
Factors such as available funding for treatment, the amount of water to be treated, the specifics of the water quality, as well as the environmental guidelines for water discharge into wetlands according to specific Acts also need to be taken into consideration.
Mine managers are also taking more notice of where water can be reused, opting more for detailed mine water-based calculations, as buying, treating and discharging mine water can be expensive, says King.
She explains that with the new calculations, mine managers are able to generate more detail on water use for mine operational models. “Mining companies therefore have significantly more knowledge and control of water use, as well as more options for reuse,” she says.
WSP offers regulatory advisory services – including analyses and consulting on how best to reduce and mitigate mine water pollution risks – in conjunction with environmental specialist services, which are specifically used to identify where and how a mining development may impact on the surrounding area.
WSP can identify the best water source options for mines, and calculate flood lines outside of which companies need to mine or place mining infrastructure in some cases. The company designs stormwater management plans focused on the separation of clean and dirty water systems, as well as dam and canal sizing and lining to prevent surface water and groundwater contamination.
The company can also identify and assess nearby wetland areas and areas within the boundary of such a regulated area, as well as design some of the management and water treatment plans to separate clean water and dirty water areas.
“We calculate static and dynamic water balances, and design and undertake dewatering plans. Thereafter, we account for the most appropriate geographical monitoring positions, the best analytical suites and the frequencies for monitoring,” King says.
WSP uses the results of these studies in conjunction with each other to identify risks, after which the company recommends mitigation measures.
“WSP can also rerate the risks where mitigation measure have been put in place,” she says.
WSP frequently assists mines with regulatory driven requirements for mine water reuse, as well as associated recommendations for infrastructure siting.
New Technologies and Legislature
“Different mines use different methods – the newer and more modern mines will adopt what could be called cleaner technologies and these would adhere to more recent environmental legislation. These technologies will include more water reuse, and less water used, in the process,” she says.
King reiterates that legislation has become stricter, and the environment’s benefiting from that has resulted in the newer and more modern mines adopting these technologies.
The commodity being mined will be a factor in determining the way in which the water will be treated, King says.
She points out that the operations of many older mines have caused extensive damage to the natural and social environment in the past, with key legacies that remain, including the acid mine drainage crisis in Johannesburg.
Acid mine drainage has resulted in the pH of the water becoming significantly low, adversely impacting on the natural environment through contamination of soil, groundwater, and surface water while causing harm to nearby local populations, including health problems.
She adds that the seriousness with which mining companies are approaching their role and responsibility in terms of the environment varies from company to company.
“The larger mining houses are more responsible because they are in the spotlight and some do feel a sense of responsibility towards the natural environment; however, some of the smaller mining companies with inadequate environmental practices go unpunished,” she says.
The consequences of mines failing to comply could result in their being fined and some mine operations being suspended for a period. In extreme cases, the mine can be shut down entirely, and those deemed responsible sent to jail, she concludes.