Let’s Talk About Acid Mine Drainage

A recent report, Remediation potential of mining, agro-industrial, and urban wastes against acid mine drainage highlights the impact of sulfide minerals, a geological byproduct of mining, on the environment; stating that when mixed with oxidising and rainfall conditions it leads to the generation of acid mine drainage (AMD), which is commonly associated with serious environmental problems worldwide.

“Acid mine drainage is problematic because of its scale, both in space and time, as it can affect both mining areas and their surroundings over large kilometres for decades or centuries,” notes the report.

The mining sector inadvertently contributes to AMD. The processes involved in mining, such as drilling, blasting, and the use of chemicals for mineral extraction, expose sulfide minerals to the environment. Once exposed, these minerals undergo oxidation reactions, producing sulfuric acid. This acid leaches into the groundwater, contaminating it with dissolved metals like iron, aluminium, and manganese.

The impact of AMD is far-reaching. Apart from environmental degradation, it also poses a significant risk to human health – heavy metals such as arsenic and lead, often present in AMD, are toxic and can lead to severe health issues. The cleanup of ADM is also extremely costly.

Like other water and wastewater (WWW) operations, AMD requires effective management to mitigate its impact. For one, contaminated water needs to be treated to neutralise acidity and remove harmful contaminants before releasing it back into the environment.

Complex water treatment plant therefore plays a critical role in managing AMD. These plants are designed to treat contaminated water from mining operations, removing impurities and adjusting the pH to safe levels.

For example, in South Africa, the eMalahleni Water Reclamation Plant – commissioned in 2010 – produces drinking water, with its feedwater coming from four coal mines in the area.

Operational efficiency

From a technological point of view, AMD plants must be managed by advanced management systems that allow for automation, monitoring and control – all vital cogs in ensuring plants run optimally:

• Industrial automation and control Systems – PLCs (Programmable Logic Controllers), offer precise control and automation of treatment processes. These systems ensure timely and accurate adjustments in response to varying water quality conditions.
• Advanced instrumentation for monitoring water quality, flow rates, and chemical composition is vital. There are several advanced instrumentation solutions available that enable real-time monitoring and control, ensuring the effective treatment of contaminated water.
• IoT-enabled platforms integrate connected products, edge control, applications, analytics, and services. It facilitates remote monitoring and management of treatment plants, enhancing operational efficiency and ensuring compliance with environmental regulations.
• Reverse osmosis systems – ideal for those or areas that require high-quality water purification, reverse osmosis systems are employed to remove dissolved salts and contaminants, producing water that meets stringent drinking standards.

Treated water can also be a valuable commodity; mining companies have the opportunity to purify AMD to potable standards and sell it to municipalities, therefore contributing to local water supplies and generating additional revenue.

AMD is a global challenge which is why it requires a concerted effort from all parties concerned. Companies such as Schneider Electric can undoubtedly improve AMD management, providing comprehensive automation and control systems to optimise operations.