Hydrogen Sulfide Removal from Biogas and Sulfur Production by Autotrophic Denitrification in a Gas-Lift Bioreactor

Biogas biodesulfurization has been successfully performed in biotrickling filters (BTFs). Nevertheless, elemental sulfur (S-0) generation and accumulation in the packed bed cause an increase in operating costs restricting its application. This drawback could be avoided using a gas-lift bioreactor as proposed in the present work, which allows recovery and reuse of the generated S-0. The effect of governing operational parameters [nitrite concentration, nitrogen/sulfur (N/S) molar ratio, hydraulic residence time (HRT), pH, inlet load (IL), and gas residence time (GRT)] was studied. Results showed that no inhibition by nitrite was found at concentrations up to 760 mg N-NO2- L-1. H2S removal efficiencies (REs) over 95% were obtained under ILs over 55 g S-H2S m(-3) h(-1) when N/S molar ratios of 1.1 mol mol(-1) or above were used. A HRT of 36 h and a pH of 7.8 +/- 0.05 were found to be optimal. The maximum S-0 production (99%) was obtained under an IL of 180 g S-H2S m(-3) h(-1) using a N/S molar ratio of 1.1 (RE = 98.1 +/- 0.5%). A maximum elimination capacity of 194.2 +/- 4.2 g S-H2S m(-3) h(-1) (RE = 83.9%) was obtained under a GRT of 41 s. Therefore, gas-lift biorcactors stand as a successful and feasible alternative to BTFs to accomplish the anoxic biodesulfurization.