Envass News

Acid mine drainage (AMD) is a prominent environmental problem which is associated with the mining industry where impacts are present in groundwater, rivers and dams. AMD occurs when sulphide minerals found in mining waste oxidises (reaction with water and air) resulting in an adverse impact on surface and groundwater sources posing a threat to humans and wildlife. The impact comprises typically of a low pH level, high salinity and elevated concentrations of sulphate content and heavy metals. Once AMD occurs it can be expensive and difficult to mitigate and control.

The conventional methods to treat AMD include physiochemical methods which involve an excessive use of chemicals. However, newer technologies that include biological treatment have been viewed as an efficient, cost-effective and eco-friendly alternative. Due to inherent variability between mines and the environmental conditions, a one treatment technique may not be effective and may require a combination of methods. The most common AMD treatment in South Africa is to aerate the water which will, in turn, oxidise the iron followed by added lime in order to increase the pH level. This treatment enables iron (and most heavy metals) to precipitate and settle out. However, generally the water contains a high sulphate content after treatment which exceeds the World Health Organization’s recommended limit.