Treatment of Acid Drainage Containing High Concentration of Ferrous Iron with Fluidized Bed Reactor

Biological oxidation of ferrous iron is useful for the treatment of acid drainage containing high concentration of ferrous iron, since a hydroxide of ferric iron easily precipitates at pH 4 by adding CaCO3. The kinetics of ferrous iron oxidation was studied in batch experiments. The effects of dissolved oxygen and initial ferrous iron concentration on the rate of ferrous iron oxidation by Thiobacillus ferrooxiadns were expressed by Monod-type equations. The best support medium for the attachment of iron oxidizing bacteria was macroporous ion exchange resin IRA938. Then, the possibility of continuous oxidation of ferrous iron was tested with a fluidized bed reactor. By use of this resin as a support medium, the continuous experiments in the fluidized bed reactor with a retention time of 20 minutes showed that more than 90 % oxidation of ferrous iron had been maintained in the duration of two months. Based on these experimental results, a mathematical model which describes the behaviour of ferrous iron in the fluidized bed reactor was developed. This model well expressed the effluent ferrous iron concentration at a steady state.