H2S oxidation coupled to nitrate reduction in a two-stage bioreactor: Targeting H2S-rich biogas desulfurization

A two-stage bioreactor operated under anoxic denitrifying conditions was evaluated for desulfurization of synthetic biogas laden with H2S concentrations between 2500 and 10,000 ppm(v). H2S removal efficiencies higher than 95% were achieved for H2S loads ranging from 16.2 to 51.9 gS m(liquid)(3)h(-1). Average H2S oxidation performance (fraction of S-SO42 produced per gram of S-H2S absorbed) ranged between 8.2 +/- 1.2 and 18.7 +/- 5.3% under continuous liquid operation. Nitrogen mass balance showed that only 2-6% of the N-NO3 consumed was directed to biomass growth and the rest was directed to denitrification. Significant changes in the bacterial community composition did not hinder the H2S removal efficiency. The bioreactor configuration proposed avoided clogging issues due to elemental sulfur accumulation as commonly occurs in packed bed bioreactors devoted to H2S-rich biogas desulfurization. (C) 2020 Elsevier Ltd. All rights reserved