Treatment of Acid Drainage from Coal Mines Produced in the Boyacá Region, Colombia, using an Anaerobic Wetland with an Upward Flow

Coal mining represents one of the primary economic incomes in the department of Boyacá, Colombia. However, the acid mine drainage (AMD) generated has a tremendous environmental impact in the area due to the presence of sulfate ions (SO4-2), heavy metals, and low pH This article studies the behavior in the content of Fe and sulfates in AMD samples when treated within an artificial anaerobic vertical flow wetland, analyzing the concentration of these elementsand the content of dissolved oxygen (DO) and pH at different time intervals. The treatment of a MAD from the department of Boyacá was carried out using a bioreactor prototype with an organic substrate to provide the necessary conditions for the development of sulfate-reducing bacteria. Measurements were made with hydraulic retention times between 24 to 120 hours, monitoring the changes in the content of total Fe, SO4-2, pH, and DO. The data obtained show a reduction for total Fe of 88.3%, established at 5.61g∙m-2∙day-1, and for SO4-2 of 34.3% with 9.35g∙m-2∙day-1; reaching a maximum removal degree of 52.32% at 120h for sulfates and 92% for Fe, where the maximum removal peak is achieved, reducing the Fe removal rate for longer times. The reduction in the concentration of Fe is related to the reduction of DO and regulation of the pH, in addition to favoring the reduction of sulfate ions through the formation of the mineralogical phases pyrite and siderite. These data show that the anoxic conditions of the organic environment are maintained, for which a subsequent aeration stage is suggested.