Sulphate removal from mine water with chemical, biological and membrane technologies

Abstract

Chemical, physical and biological technologies for removal of sulphate from mine tailings pond water (8 g SO/L) were investigated. Sulphate concentrations of approximately 1,400, 700, 350 and 20 mg/L were obtained using gypsum precipitation, and ettringite precipitation, biological sulphate reduction or reverse osmosis (RO) after gypsum pre-treatment, respectively. Gypsum precipitation can be widely utilized as a pre-treatment method, as was shown in this study. Clearly the lowest sulphate concentrations were obtained using RO. However, RO cannot be the only water purification technology, because the concentrate needs to be treated. There would be advantages using biological sulphate reduction, when elemental sulphur could be produced as a sellable end product. Reagent and energy costs for 200 m/h tailings pond water feed based on laboratory studies and process modelling were 1.1, 3.1, 1.2 and 2.7 MEur/year for gypsum precipitation, ettringite precipitation, RO and biological treatment after gypsum precipitation, respectively. The most appropriate technology or combination of technologies should be selected for every industrial site case by case.

Technology of the comprehensive desalination of wastewater from mines

“…The capacity of the weakly acidic cation exchanger for hardness ions is quite high, independent of the concentration of sodium ions in the solution. At the concentration of sodium chloride of ≈29 g/dm 3 , full exchange dynamic capacity for hardness ions in the cation exchanger DOWEX MAC-3 reaches 3,000 mg-equiv./dm 3 . Thus, DOWEX MAC-3 makes it possible to soften water effectively in order to ensure the stabilizing treatment of water before its baromembrane desalination.…”

“…There are many methods to purify mineralized wastewater, which include reagents-based, ion-exchange, membrane, electrochemical, biological, and others. The authors of [3] compared different methods to purify water from sulfates. It is shown that in the purification of water with the original concentration of sulfates 1,400, 700, 350, and 20 mg/dm 3 , the most effective was the reverse osmosis.…”

“…Thus, membrane technologies have a significant disadvantage [3][4][5][6][7][8]. The result of reverse osmotic treatment is the large volumes of concentrates, characterized by the elevated concentration of sulfates and hardness ions.…”

“…To recycle the concentrates from baromembrane purification, it is proposed to use the biological reduction of sulfate to sulfur [3]. The main disadvantage of a given method is the high sensitivity of biological methods.…”

“…Mineralization of coal-mining waters varies from 1-3 to 20-30 g/dm 3 . Therefore, our research is aimed at the desalination of weakly and highly mineralized waters for obtaining drinking water for people or technical water for the needs of the industry.…”