Acid mine drainage prevention using mushroom compost as organic amendment

The Acid mine drainage (AMD) are discharges characterized by low pH and high concentrations of sulfate and metals. AMD is considered as a serious problem of the mining industry and preventing its formation is the best environmental and economical option. Mushroom compost was evaluated as organic carbon amendment to promote sulfate reduction and metal sulfide precipitation during AMD formation. Three PVC cells (2.4 L) were filled with 300 g of the mixture of mushroom compost and coal mining waste in different proportions (40:60, 25:70, 60:40 %) and 400 mL of water (18,5 Ω). The chemical change in the leachates and the microbial activity in the mixtures were evaluated for 6 weeks. In leachates, dissolved oxygen (< 2,0 mg L-1) and redox potential (< -100 mV) decreased while pH (> 6,5) and alkalinity (> 1500 mg CaCO3 L-1) increased. Besides, all mixtures were efficient for metals precipitation (Fe2+ > 95%; Mn2+ > 96%; Zn2+ > 52%) and sulfate reduction (> 50%). However, a significant production of sulfide and a greater microbial activity was observed in the mixture of mushroom compost and coal mining waste 25:75, indicating the presence of sulfate-reducing bacteria. The results showed that mushroom compost could be used as organic carbon amendment to prevent AMD generation and that the mixture 25:75 could be a promising option to be used in Zipaquirá Mining District (Colombia).