H_2S oxidation coupled to nitrate reduction in a two-stage bioreactor: Targeting H_2S-rich biogas desulfurization

摘要

A two-stage bioreactor operated under anoxic denitrifying conditions was evaluated for desulfurization of synthetic biogas laden with H_2S concentrations between 2500 and 10,000 ppm_v. H_2S removal efficiencies higher than 95% were achieved for H_2S loads ranging from 16.2 to 51.9 gS m_(liquid)~(-3)h~(-1). Average H_2S oxidation performance (fraction of S-SO_4~(2-) produced per gram of S-H_2S 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_3~- consumed was directed to biomass growth and the rest was directed to denitrifica-tion. Significant changes in the bacterial community composition did not hinder the H_2S removal efficiency. The bioreactor configuration proposed avoided clogging issues due to elemental sulfur accumulation as commonly occurs in packed bed bioreactors devoted to H_2S-rich biogas desulfurization.