Model-based analysis of microaeration for biogas desulfurization using a biomembrane

Hydrogen sulfide gas is an undesirable product of anaerobic treatment of sulfate-rich wastewater, which must be removed from biogas before burning the latter in a cogeneration unit. Microaeration is a biological desulfurization method, which consists in dosing small amount of air into anaerobic digester to support the growth of sulfide oxidizing bacteria (SOB) and the formation of elemental sulfur. The use of a so-called biomembrane, on which SOB grow, has recently been proposed as a promising process option that avoid biogas dilution with nitrogen from the dosed air as well as possible clogging of pipes by the elemental sulfur formed. In this study, the biomembrane-based microaeration processes was analysed through mathematical modelling and simulation. A mathematical model describing biogas desulfurization by microaeration through a biomembrane was presented for the first time. The model was validated to fit lab-scale experimental data as well as to represent a pilot-scale system. A sensitivity analysis showed that mass transfer coefficient and membrane surface area were the most important parameters in biofilm compartment affecting process kinetics. Additionally, important role of chemical oxidation of hydrogen sulfide was confirmed by the simulation results.