Tatsuo Omura

BIOLOGICAL FERROUS-IRON OXIDATION WITH FLUIDIZED BED REACTOR

ABSTRACT The kinetics of ferrous iron oxidation by iron oxidizing bacterium Thiobacillus ferooxidans was studied in batch experiments. The effects of dissolved oxygen and initial ferrous iron concentration on the rate of ferrous iron oxidation could be expressed by Monod-type equations. The maximum specific oxidation rate was 3.6 × 10 −9 mg/h/cell and saturation constants with respect to ferrous iron and dissolved oxygen were 140 mg/1 and 0.162 mg/1, respectively. Among the support materials studied, the macroporous ion exchange resin Amberlite IRA-938 had the best attachment of iron oxidizing bacteria. By use of this resin as a support medium, continuous experiments with a fluidized bed reactor were carried out to study a biological oxidation of ferrous iron. An over 90% efficiency of ferrous iron oxidation was obtained at influent ferrous iron concentrations of 0.5 and 1.0 g/1 within a range of hydraulic retention times of 0.4–2.5 hrs. On the basis of these experimental results, mathematical models were developed to describe the behaviour of ferrous iron concentrations in the support media and in the fluidized bed reactor. These models well expressed ferrous iron concentrations in the effluent.