A sustainable approach for the mine water treatment

Mine water treatment can be seen as challenging, but also a long-term task. In addition to better known acidity correction and heavy metals and metalloids removal, the mine water treatment approaches are slowly shifting to advanced methods, targeting the elimination of the salinity. Some methods for the sulfate and calcium removal are advancing to industrial implementation (e.g. ettringite precipitation, membrane separation and combinations of these methods), but the cost is high and the cost to benefit result may be controversial. On other hand, the seeded crystallization of gypsum can lower the sulfate and calcium concentration after conventional treatment by liming. Despite that this technique is limited by the gypsum solubility, it is bringing considerable benefits as a second treatment stage after the conventional liming, by safely lowering the sulfate concentration from 2000...4000 mg/L to about 1500 mg/L, together with the equivalent calcium quantity. Due to the fact that this method is using recycled gypsum produced within the process, it can be seen as a sustainable practice. This is illustrated by a case study for a mine water source with an initial sulfate content of about 5000 mg/L.