Importance of digester’s headspace geometry for the efficient H2S removal through microaeration; experimental and simulation study

[Display omitted] •Modifying headspace geometry affected the position of biofilm growth.•Modifying headspace geometry did not deteriorate microaeration efficiency.•CFD model described the flow of biogas and oxygen above the rotating liquid.•The oxygen required for H2S oxidation depends on the position of oxygen injection.•Well-designed headspace helps localize sulfur deposition and decrease oxygen needs. Microaeration for biogas desulfurization occurs mainly in the headspace of anaerobic digesters where the biofilm growth is mainly reported; however, no study has been focused on the effect of headspace geometry on microaeration performance. This research evaluates the effect of headspace geometry on biogas flow, subsequent biofilm growth, and the effect of these parameters on microaeration efficiency. This effect was studied in an anaerobic digester with three different headspace configurations. Also, the computational fluid dynamics (CFD) model explained the experimental results. The CFD model developed described the biogas flow in all headspace configurations. It was proven that the modifications of headspace geometry altered biogas flow and avoided biofilm growth on the reactor walls leading to the reactor's protection from the adverse effects of biofilm growth. The mathematical model developed in this work can help design microaerobic digesters or find the best way to implement microaeration into the digesters already built.