Efeito das concentrações de sulfato e ferro, do doador de elétrons e da razão DQO/SO42- no tratamento de drenagem ácida de mina em reatores operados em batelada

Abstract

The high acidity presented by acid mine drainage (AMD) can promote the dissolution of metals resulting in negative consequences and impacts on health and the environment. Biotechnological treatments involving sulphate reduction have advantages over traditional physicochemical treatments, such as the removal and the possibility of recovering the metals present in this residue, lower costs of disposal of the generated sludge and generation of alkalinity to increase the pH of these effluents. Biological reduction of sulfate, carried out by sulfate-reducing bacteria with the addition of exogenous carbon sources, occupies a prominent place among the alternatives, as it combines the increase in pH with the removal of sulfate and metals and generates good efficiency and viability cost-effective for treatment. This study, we sought to optimize the efficiency of sulfate removal present in synthetic DAM using anaerobic batch reactors during 6 phases in which different carbon sources, sulfate and iron concentrations were tested, in addition to different chemical oxygen demand (COD)/SO42- ratios. and increasing the scale of the reactor. In each of the phases, concentrations of COD, sulphate, initial and final pH, alkalinity, sulphide and iron concentration were analyzed, and total, fixed and volatile sludge solids. The best condition used in each phase was kept for the next phase and new conditions were tested in order to obtain, at the end of 5 phases, the best reactor configuration. At the end of the first 5 phases, in which reactors with a useful volume of 500mL were used, a reactor with a larger volume of 2.5L was set up. The condition containing whey, 1500mg/L of sulfate, 100mg/L of iron and COD/SO42- equal to 1 had the best removal efficiencies, ranging from 59% to 81% for sulfate removal and 77% to 96 % for COD removal, in addition to a final pH ranging from 6.6 to 6.7. However, in the larger volume reactor, the lack of agitation affected the performance and the removal was lower, reaching 42% and 77% of sulfate and COD removal efficiency, respectively. Furthermore, the results of this study showed high robustness of the inoculum used, since, even submitted to different treatments, there was no impact on removal efficiencies.