Fully aerobic two‐step desulfurization process for purification of highly H2S‐laden biogas

BACKGROUND A two‐step desulfurization technology coupling an absorption column with an airlift bioreactor (ALR) provided with continuous aeration was studied. This setup allowed the full oxygenation of the liquid phase, overcoming the typical issues of aerobic biotrickling filters such as elemental sulfur accumulation, biogas dilution or generation of explosive mixtures. RESULTS Removal efficiencies of 100% were achieved under all the S‐H2S inlet loading rates tested (28, 56 and 112 gS‐H2S m−3 h−1). The main sulfur compound in the liquid phase was SO42− regardless of the inlet load tested with and average sulfur oxidation performance of ∼80%. The robustness of the desulfurization system over a 7‐days shutdown period was also evaluated. H2S removal efficiency of 100% was recorded only 10 h after restarting the system without H2S stripping from the ALR. The microbial communities present in the inoculum and those established in the desulfurization system at the end of the experimental time were characterized by 16S rRNA pyrosequencing. CONCLUSION Biogas laden with H2S concentrations ranging from 2500 to 10 000 ppmv was successfully desulfurized in the fully aerobic two‐step process presented. High and stable removal performance was achieved even after a long‐term shutdown period. © 2018 Society of Chemical Industry