IRON REMOVAL FROM ACID MINE DRAINAGE BY AN ACIDOPHILIC PROTOZOAN

Iron removed from an artificial acid mine drainage (AMD) solution by the acidophilic, photosynthetic protozoan, Euglena mutabilis, was evaluated in the laboratory. E. mutabilis forms benthic mats in AMD systems in Indiana, and plays an important role in the natural recovery of contaminants, specially iron, by (1) increasing the concentration of dissolved oxygen in the water, which enhances the rate of inorganic precipitation of reduced metal species (including Fe²⁺), and (2) sequestering and storing iron intracellularly.

An artificial AMD media with 27 mg/l iron was placed in 12 sterile tubes, each tube containing 20 ml. Eight tubes were inoculated with E. mutabilis and the remaining tubes were kept as uninoculated controls. Each month for four months two inoculated samples and one control sample were filtered to remove precipitates and microbes, and then analyzed for iron using inductively coupled plasma spectrometry (ICP). Results of the analysis indicate a faster rate of iron removal in tubes containing E. mutabilis. Iron concentrations in the remaining final analyses showed approximately 0.5 mg/l in the inoculated samples, and 12.2 mg/l in the control sample. In addition, samples with E. mutabilis contained higher quantities of precipitate, based on visual estimations. These high quantities were confirmed by weighting the precipitates in the inoculated samples versus the controls; however, the inoculated samples also included the weight of E. mutabilis cells.