Acid mine drainage (AMD) in the Gauteng City-Region (GCR) has been largely described in the media as a ticking time bomb after it was officially reported to have begun surfacing from old mining works on the West Rand in 2002. AMD from abandoned mine shafts and dumps poses a threat to clean water, as the contaminated water seeps into both surface and underground water reserves.
Although government has shown a commitment to dealing with AMD through initiating a R150 million fund to tackle the problem, most researchers believe that this will not be enough to solve the problem as there are more than 6000 abandoned mine shafts, that require a budget of R30 billion to solve acid mine drainage in the Witwatersrand region.
The environmental problem associated with centuries of mining in the country cannot be understated. Mountains of waste mine dumps and webs of abandoned mining shafts harbour iron pyrite known as “fool’s gold”, which reacts with rainwater and groundwater to create sulphuric acid.
So what exactly is AMD? Simply put, AMD is the flow of unsafe, polluted, acidic water from old mining areas. The level of pollutants in the water mostly depends on the area it comes from. The water may contain high levels of salts, sulphate, iron, aluminium, toxic heavy metals such as cadmium and cobalt, and at times radioactive elements. This contaminated water is capable of polluting soil and water supplies as it spreads underground and flows into streams and rivers.
Geologists claim the contaminated water reaches up to 350 million litres per day, and flows in the greater river catchment area of the Vaal and Limpopo rivers.
The flow of AMD into South Africa’s surface and ground water systems is having devastating and lasting consequences that are both far-reaching and long-term. These consequences include degrading the quality of the country’s water systems, poisoning of food crops, destroying wildlife and eco-systems, endangering human health and infrastructure and heritage sites.
In addition to these challenges, the increase in population, urban industrial expansion, persistent droughts and the shortages of clean water call for a revolutionary approach in water management.
This situation prompted the Department of Water Affairs to intervene by setting up a water treatment plant in the particularly heavily polluted Brugspruit area near Witbank. This intervention has been of limited efficiency. The attempt mainly focused on addressing the acidity levels of the water and had little effect on the heavy metals and salinity of the water.
It is against this background that comprehensive efforts need to be applied to ensure long term sustainable mining business practice to generate value for the economy, as well as for communities that are affected by mining operations.
New technology coming out of DOW Southern Africa, is offering a solution to this problem.
Through Dow Water and Process Solution, Dow Southern Africa offers world class enabling component technologies designed to advance the science of water treatment, purification of acid mine drainages for water reuse, seawater desalination and specific contaminant removal from polluted water through nanotechnology.
While Reverse osmosis technology has been in the industry for decades, DOW brings in advanced technologies that combine reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) membranes, and ion exchange resins.
According to Ross Maclean, President of DOW Southern Africa, the advancement allows “mine operators to optimise their water management, by extracting, separating and purifying metals, while also assisting them to reduce waste and recycle reagents”. Ensuring the treated mining wastewater can be reused for other business purposes and also for drinking water.
South Africa has the most industrialised and diverse economy in Africa, such that networks of industries in South Africa make it possible for companies to create synchronised service around mining areas through using the latest technology of RO and UF. Maclean argues that their new technology allows the commitment to produce the quality of end product water that meets the specification standard for which the reuse is intended for.
“For example power stations need a certain purity of water in the steam turbines. Today, you can set up with a supply of recycled water from a mine to generate power,” he explains.
Coal mining in South Africa has historically centered in the Mpumalanga province, east of the city of Johannesburg. Many years of coal mining for power generation, and other local uses has resulted in an extensive network of operating and abandoned opencast mines that span the region. According to McLean, AMD in these derelict coal fields is also formed in a similar way to that observed in gold mines. DOW Southern Africa has used its technologies in plants built to treat coal mining drainage wastewater so it can be reutilised for power generation around the coal mines to save energy.
Waste water from the mine is set to a standard where it can be recycled and used in the power station, and finally treated for reuse in irrigation.
Dow’s technology has the benefit of being able to produce safe water with zero discharge by removing heavy metals in mining wastewater. In addition, the technology offers value in the secondary extraction and recovery of valuable metals from water seepages thereby reducing environmental hazards while at the same time sustaining business.
The use of technology that combines reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) membranes, and ion exchange resins and the research behind the scenes are steps in the right direction towards treating AMD. These efforts might ultimately lead to a stronger society and AMD might just become a problem of the past, in the near future.