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

A two-stage bioreactor operated under anoxic denitrifying conditions was evaluated for desulfurization of synthetic biogas laden with HS concentrations between 2500 and 10,000 ppm. HS removal efficiencies higher than 95% were achieved for HS loads ranging from 16.2 to 51.9 gS mh. Average HS oxidation performance (fraction of S-SO produced per gram of S-HS 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-NO consumed was directed to biomass growth and the rest was directed to denitrification. Significant changes in the bacterial community composition did not hinder the HS removal efficiency. The bioreactor configuration proposed avoided clogging issues due to elemental sulfur accumulation as commonly occurs in packed bed bioreactors devoted to HS-rich biogas desulfurization.