Removal sulfate and metals Fe+2, Cu+2, and Zn+2 from acid mine drainage in an anaerobic sequential batch reactor

Acid mine drainage (AMD) features a significant environmental problem due the production of acidic solution generated by the oxidation of mining waste. Accordingly, there is constant necessity for treatment technologies and processes to make likely residue to be launched of aquatic system without changing water quality. The use of anaerobic sequential batch reactor (ASBR) for AMD treatment has shown to be a viable alternative, as sulfate reducing bacteria (SRB) reduce sulfate ions to sulfide that may precipitate metals presents in solution or oxidize sulfide produced to elemental sulfur. An ASBR with 7 L was operated at 30 degrees C for the treatment of synthetic AMD containing SO4 2-1500 mg/L, with ratio COD/Sulfate equal 1 and ethanol as carbon source for 270 days with 6 phases containing different concentrations of metals (100-400 mg L-1 of Fe2+, 20-40 mg L-1 of Zn2+, 5-10 mg L-1 of Cu2+), based on values with potential toxicity to SRB. During the operation phases the concentration of metals gave an increase in removal SO42-. COD removal ranged from 68.4 to 94.4% and sulfate from 39.1 to 72.8%. The Fe2+ removals were above 99.2%, Zn2+-100% and Cu2+ above 93.3%. Given the high removal metals and SO42-, ASBR characterized a form suitable for the AMD treatment.