High efficiency reactor for the biooxidation of ferrous iron

The biooxidation of ferrous iron is a potential industrial process in the regeneration of ferric iron, in hydrometallurgical leaching operations and in the removal of H2S in combustible gases. Another field of application is the treatment of acid mine drainage water. The aim of this work was the design of a continuous reactor for a high efficiency ferrous iron biooxidation capable of attaining the oxidation rates demanded by industrial processes for a minimum-sized reactor. Some criteria of design come from the data of former studies. The bioreactor consists of a 1249 mm high and 84 mm diameter column randomly packed with siliceous stone particles with inlets for fresh medium and air at the bottom. The present work studies the influence of air and liquid flow rates on the ferrous iron biooxidation in a flooded packed bed bioreactor. Starting from the data of this study, kinetics, and oxygen concentration in the outlet gas, it was deduced that the biooxidation process was limited by the availability of oxygen in the liquid medium. The free-swimming cells concentration was measured in the outlet solution for different operating conditions. It was observed that once the biofilm has been formed, a variation in the liquid flow rate does not alter the biomass attached to the packing. The highest ferric productivity attained was 11.25 g/L·h.