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RESEARCH PRODUCT

Fully aerobic bioscrubber for the desulfurization of H2S-rich biogas

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Abstract A fully aerobic bioscrubber for the desulfurization of H2S-rich biogas was developed in the present study by coupling an absorption column and a bubble column bioreactor. The bioscrubber treated H2S loading rates of 37, 59, and 100 g S mliquid−3 h−1 at gas residence times of 6.6, 4.1 and 2.4 min in the absorption column, respectively. Stable H2S removal efficiencies above 80% were recorded at all the conditions tested. The bioscrubber was robust towards short- and long-term operation shutdowns (5 and 18 days), the H2S removal performance being recovered after few hours. The aerated bubble column bioreactor was operated at slightly alkaline conditions (pH 8 ± 0.5), which prevented H2S stripping and allowed sulfur oxidation performances higher than 75% regardless of the operating conditions tested. Bacterial community characterization by 16S rRNA pyrosequencing revealed that the operating conditions (slightly alkaline pH, sulfate concentrations of up to 25,000 g m−3 and dilution rates of 5.7 × 10−3–8.6 × 10−3 h−1) shaped a specialized community highly efficient for H2S oxidation. Three Proteobacteria were predominant in the bubble column bioreactor, namely Thioalkalimicrobium cyclicum, Stappia sp. and Ochrobactrum sp. with relative abundances of 68.18, 13.49 and 7.61%, respectively.