Experimental study on the treatment of acid mine drainage by modified corncob fixed SRB sludge particles

In view of the characteristics of high content of SO₄ ^2-, Fe²⁺ and Mn²⁺ in acid mine drainage and low pH value, based on the microbial immobilization technology, the single factor test and the orthogonal test were set respectively to determine the optimum alkaline H₂O₂ modification conditions for corncob. Then combining with sulfate reducing bacteria sludge, the modified corncob immobilized SRB sludge particles were prepared to treat acid mine drainage. On this basis, three dynamic column test models, including Column 1 without corncob particles, Column 2 with unmodified corncob particles, and Column 3 with modified corncob particles, were constructed. Through dynamic experiments, the three dynamic columns were compared to study the efficacy of AMD and their ability to resist changes in pollution load. The results of the orthogonal experiment showed that: when the corncob modified time was 24 h, the concentration of NaOH was 6% and the concentration of H₂O₂ was 1.5%, the prepared immobilized particles performed best. The results of the dynamic test showed that the treatment effect of Column 3 on AMD was better than that of Column 1 and 2. In the dynamic tests before and after the increase of pollution load, the highest removal percentages of SO₄ ^2-, Mn²⁺, Fe²⁺ in Column 3 were 72.65%, 56.72%, 62.47% and 62.58%, 30.07%, 46.87% respectively, the average COD emission was 234 mg L^-1 and 102.75 mg L^-1, the effluent pH value was 6.96 and 6.65. In the dynamic tests before and after the increase of pollution load, the highest removal percentages of SO₄ ^2-, Mn²⁺, Fe²⁺ in Column 2 were 52.94%, 46.93%, 72.55% and 48.92%, 26.43%, 43.23% respectively, the average COD emission was 508.14 mg L^-1 and 152.88 mg L^-1, the effluent pH value was 6.56 and 6.36. The high COD value of Column 2 is due to the organic matter leakage and poor metabolic activity of SRB contained in immobilized particles. Therefore, it indicated that Column 3 could better treat pollutants and resist changes of pollution load.