Key parameters influencing hydrogen sulfide removal in microaerobic sequencing batch reactor

In industry, microaeration is often used for the removal of hydrogen sulfide (H2S) from biogas in full-scale biogas plants. This strategy is very successful when applied in a continuous stirred tank reactor (CSTR), but, due to the fluctuating concentration of H2S in biogas, it is challenging to achieve consistently high H2S removal in an sequencing batch reactor (SBR) or intermittently mixed and/or fed CSTR. To optimize air/oxygen dosing, key parameters influencing the biochemical removal of H2S under microaerobic conditions must be quantified. Here, a lab-scale microaerobic SBR was operated under mesophilic conditions to assess these parameters. In parallel, a mathematical model describing the kinetics of sulfur transformation was developed in AQUASIM software. The experimental data were used to calibrate the model. Subsequent sensitivity analysis identified the liquid-to-gas mass transfer coefficient and biofilm area as the key parameters. We show that the optimization of these parameters is crucial if microaeration is to be successfully utilized for H2S removal from biogas in intermittently mixed reactors.