Experiment on the treatment of acid mine drainage with optimized biomedical stone particles by response surface methodology.

The immobilized particles were used to treat acid mine drainage (AMD) in the study, which owns the characteristics of serious pollution and high managing cost. The immobilized particles were prepared with sulfate reducing bacteria (SRB) and medical stones. In order to investigate the interactive influence of medical stones on the particle properties, the salt modification condition, content, and size of the medical stone were taken as the influential factors. At the same time, the removal rate of SO42- and Mn2+, the release of total irons (TFe) and chemical oxygen demand (COD) and pH value were taken as the response values in the experiment. On the basis of the orthogonal experimental research, a response surface model was established. The experimental analysis showed that the particles can get the best treatment effect, when using the salt-modified medical stone with the content of 15% and particle size of 200~300 mesh. At this time, the removal rates of Mn2+ and SO42- in wastewater were 83.10 and 96.22%, respectively. The release contents of TFe and COD were 2.99 mg L-1 and 1828.54 mg L-1, respectively, and the pH value was 7.05. Then, biological medical stone particles were prepared according to the optimal ratio in the response surface experiment. The adaptability of biomedical stone particles was studied at different concentrations of SO42-, Mn2+ and pH value. The results showed that the high concentration of SO42- inhibited the metabolism of SRB, while Mn2+ had a less effect. The biomedical stone particles could regulate pH value very well.