In situ biotreatment of acidic mine drainage using straw as sole substrate

Abstract

Feasibility of using straw as sole substrate for in situ bioremediation of acidic mine drainage (AMD) was studied. The result showed that straw was more suitable than woodchips, which had been successfully used for bioremediating AMD at the source, for establishing bioremediation layer. The sulfate removal rate of rice straw treatment was almost two times higher than that of the woodchips treatment when the initial pH of the synthetic AMD was set to 3.0. Straw treatment may be more efficient at reducing sulfate than woodchips treatment under stressful conditions. The sulfate removal rate of the rice straw treatment increased from 8.67 to 21.77 mg L−1 day−1 when initial pH increased from 1 to 7 while the removal rate of woodchips treatment increased from 3.80 to 11.95 mg L−1 day−1. The sulfate removal rate of the rice straw treatment decreased from 13.93 to 9.91 mg L−1 day−1 when temperature decreased from 25 to 5°C while the removal rate of woodchips treatment decreased from 7.43 to 4.98 mg L−1 day−1. Differences in soluble organic carbon release between rice straw and woodchips led to the differences in bioremediation efficiency. Concentrations of Cu2+ maintained at low level in the column effluent during the whole bioremediation period. Cu2+ was removed by forming sulfide precipitates. Microbial community analysis showed that sulfate reducing bacteria in the bioremediation layer together with microorganisms capable of degrading rice straw caused the bioremediation of AMD. These findings have significant environmental implications in terms of in situ bioremediation of AMD using straw as sole substrate.