Trials for the improvement of the ettringite process for the mine water treatment

Mine water from abandoned mines and spoil heaps from closed mining perimeter may generate significant surface water pollution. In Romania there are tens of sources with moderate to high contamination. Mine water flows have to be treated to meet national regulation NTPA 001/2005 for discharging in surface waters as any wastewater in any water body: low limits for heavy metals, but also for species considered benign to a certain level – calcium, magnesium and sulfate. By lime precipitation treatment, some CaSO4 can be formed, lowering the [SO42–] level, but the limit for sulfate will not be achieved, because the concentration correlated to gypsum solubility exceeds it by roughly three times. Sulfate precipitation as ettringite is a robust multi-stage technology (ECOIND- WISUTEC 2007–2012), but the costs are not reasonably sustainable for long term. Some approaches for modified technological flow-sheets and laboratory test result for the valorisation of reactive aluminium sources (e.g. mine water aluminium or flows with wasted aluminium).