RESUMEN
Actual acid mine drainage (AMD) containing a high concentration of sulfate (â¼1,000 mg·L-1), dissolved metals, uranium, rare earth elements and yttrium (REY) was treated using a down-flow fixed-structured bed biological reactor (DFSBR). The reactor was operated in a continuous flow mode for 175 days and the temperature was maintained at 30 °C. The synthetic AMD was gradually replaced by the actual AMD in 20, 50 and 75% of the total medium volume. Sugarcane vinasse was used as the electron donor and the influent pH of the reactor was decreased from 6.9 to 4.6 until the system collapsed. REY elements and transition metals were removed from the actual AMD and precipitated in the down-flow fixed-structured bed reactor. Sulfate reduction achieved 67 ± 22% in Phase II and chemical oxygen demand (COD) removal was above 56% in Phases I and II. Removal of La, Ce, Pr, Nd, Sm and Y was higher than 70% in both Phases II and III while Fe, Al, Si and Mn were removed with efficiencies of 79, 67, 48 and 25%, respectively. The results highlighted the potential use of DFSBR in the treatment of AMD, providing possibilities for simultaneous sulfate reduction and metal and REY recovery in a single unit.
Asunto(s)
Metales de Tierras Raras , Itrio , Ácidos , Reactores Biológicos , Concentración de Iones de Hidrógeno , Metales , MineríaRESUMEN
This paper discusses the results of pentachlorophenol (PCP) anaerobic biodegradation in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor operated under methanogenic and halophylic conditions. The system was inoculated with autochthonous microorganisms taken from a site in the Santos-São Vicente Estuary (state of São Paulo, Brazil) severely contaminated with PCP, phenolic compounds, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and heavy metals. The inoculum was previously enriched for methanogenesis activity by changing glucose concentrations and under halophylic condition. PCP was added to the HAIB reactor as sodium salt (NaPCP) at an initial concentration of 5 mg l(-1) and increased to 13, 15, and 21 mg l(-1). Organic matter removal efficiency ranged from 77 to 100%. PCP removal efficiency was 100%. Denaturing gradient gel electrophoresis profile showed changes in the structure of Bacteria domain, which was associated with NaPCP and glucose amendments. The diversity of Archaea remained unaltered during the different phases. Scanning electron microscope examinations showed that cells morphologically resembling Methanosarcina and Methanosaeta predominated in the biofilm. These cells were detected by fluorescence in situ hybridization with the Methanosarcinales (MSMX860) specific probe. The results are of great importance in planning the estuary's restoration by using anaerobic technology and autochthonous microorganisms for bioremediation.