The Effect of Oxygen Supply on the Dual Growth Kinetics of Acidithiobacillus thiooxidans under Acidic Conditions for Biogas Desulfurization

In this study, to simulate a biogas desulfurization process, a modified Monod-Gompertz kinetic model incorporating a dissolved oxygen (DO) effect was proposed for a sulfur-oxidizing bacterial (SOB) strain, Acidithiobacillus thiooxidans, under extremely acidic conditions of pH 2. The kinetic model was calibrated and validated using experimental data obtained from a bubble-column bioreactor. The SOB strain was effective for H(2)S degradation, but the H(2)S removal efficiency dropped rapidly at DO concentrations less than 2.0 mg/L. A low H(2)S loading was effectively treated with oxygen supplied in a range of 2%–6%, but a H(2)S guideline of 10 ppm could not be met, even with an oxygen supply greater than 6%, when the H(2)S loading was high at a short gas retention time of 1 min and a H(2)S inlet concentration of 5000 ppm. The oxygen supply should be increased in the aerobic desulfurization to meet the H(2)S guideline; however, the excess oxygen above the optimum was not effective because of the decline in oxygen efficiency. The model estimation indicated that the maximum H(2)S removal rate was approximately 400 ppm/%-O(2) at the influent oxygen concentration of 4.9% under the given condition. The kinetic model with a low DO threshold for the interacting substrates was a useful tool to simulate the effect of the oxygen supply on the H(2)S removal and to determine the optimal oxygen concentration.