Redução do sulfato e remoção de metais provenientes de drenagem ácida de mina

Abstract

The search for solutions to achieve sulfate removal from acid mine drainage (AMD) using anaerobic stirred batch reactor (ASBR) demands research and development. The mining industry, although extremely necessary to the human development, has a strongly negative characteristic due to the high quantity of residues generated in its process. The problem is emphasized when the processed ore is sulfide base and its residue, in contact with oxygen and water, produces a wastewater named acid mine drainage (AMD), characterized by high acidity (low pH) and the presence of dissolved heavy metals and sulfate. This process is catalyzed by bacteria existing in the environment. In this work was used a bioremediation technology to treat the AMD where the sulfate reducing bacteria (SRB) through their own dissimilatory metabolism are able to generate alkalinity, increasing the environmental pH, remove sulfate and settle existing metals in the solution due to the reaction with the sulfide generated in the process. In this work was used an ASBR operating with COD/SO42- ratio equal to 1.0 and using ethanol as source of carbon and electron donor. Along more than 200 days of the ASBR operation, aspects such as adaptation and operation adding Fe2+, Zn2+ and Cu2+ were evaluated operating with cycles of 24 and 48 hours. The initial pH was kept around 4.0 along all the experiment. The average value ranges achieved were: pH effluent – 6.5 to 7.4; SO42- removal - 43 to 65 %; DQO removal – 66 to 90%; sulfide concentration – 3.7 to 56.6 mg.L-1 and removal of Fe2+, Zn2+ and Cu2+ were higher than 99 %.