Sulfate Removal from Extremely Acidic Wastewaters Using Consortia of Acidophilic Sulfate-Reducing Bacteria

A low pH sulfidogenic bioreactor, maintained between pH 2.8 and 4.0, was used to lower sulfate concentrations in two extremely acidic (pH 1.3 to 3.0) synthetic mine waters that contained ferrous iron but no other chalcophilic metals. Tests with water carried out with synthetic mine water from a German site showed that 98% of the sulfate present could be removed by manipulating the water pH and concentration of electron donor (glycerol) for the sulfate-reducing bacteria. While more sulfate was removed with synthetic Chilean mine water (up to 35 mmoles L -1 ), this only accounted for between 50-60% of the total present. There was close agreement between the stoichiometry of glycerol used and the amount of sulfate removed, particularly with the German mine water.