Oxygen mass transfer requirements during ferrous iron oxidation by Thiobacillus ferrooxidans under controlled pH conditions

Abstract

The ferrous iron oxidation by the bacterium Thiobacillus ferrooxidans B5 was studied under different aeration conditions at constant pH (1.8 and 2.0) in three types of bioreactors (shake flasks, a bubble column and a stirred tank). The main goal was to reflect the effects of the method and the intensity of agitation and/or aeration on ferrous iron biooxidation. The specific growth rates and the substrate oxidation rate constants in the exponential phase were actually the same (0.069 ± 0.002 h -1 ), regardless of the bioreactor type and the pH condition, if the oxygen transfer rate was higher than approximately 1.0 mg O 2 /L/min. The maximum biooxidation constants were affected by the oxygen transfer only at lower aeration intensities. Thus, the oxygen transfer rate could be used as a basis for scaling-up bioreactors for the ferrous iron biooxidation by T. ferrooxidans under aerobic and controlled pH condition.