Sulphate removal technologies for the treatment of mine-impacted water

Abstract

Mine-impacted water, including acid mine drainage (AMD), is a global problem. While precipitation of dissolved metals and neutralization of acidity from mine-impacted water is accomplished relatively easily with lime addition, removal of sulphate to permissible discharge limits is challenging. This paper presents a high-level comparison of four sulphate removal technologies, namely reverse osmosis, ettringite precipitation, barium carbonate addition, and biological sulphate reduction. Primarily operating costs, based on reagent and utility consumptions, are compared. Each process is shown to be subject to a unique set of constraints which might favour one over another for a specific combination of location and AMD composition. Access to and cost of reagents would be a key cost component to any of the processes studied. The total cost calculated for each process also depends on the type of effluents that are allowed to be discharged.

Recent Progress on Acid Mine Drainage Technological Trends in South Africa: Prevention, Treatment, and Resource Recovery

“…Finally, in the fifth stage, the remaining water from stage four is treated with carbon dioxide to lower the pH and remove calcite by precipitation. The advantages of the SAVMIN process include high-quality by-products such as metal hydroxides, gypsum, and calcite which can potentially be resold to enhance the economic feasibility of this treatment [17,101]. However, again, it too produces significant amounts of waste sludge that would need to be disposed of.…”

“…Some metal mining effluents contain high levels of poisonous cyanides and heavy metals, which have major human health and environmental consequences [3,11,12]. To remediate AMD, many wastewater treatment technologies have been used, including neutralization [13], selective precipitation [14], use of membranes [15], exchange of ions [16], and the removal of sulphate biologically [17]. The challenge, however, is that the constituents of AMD, while hazardous, may be collected and turned into valuable materials that can be commercialized.…”