H2 addition through a submerged membrane for in-situ biogas upgrading in the anaerobic digestion of sewage sludge

• Published in: Bioresource technology 2019-05, Vol.280, p.1-8
• Main Authors: Alfaro, Natalia, Fdz-Polanco, María, Fdz-Polanco, Fernando, Díaz, Israel
• Format: Article
• Language: English
• Subjects: acetogens; anaerobic digesters; anaerobic digestion; biogas; carbon dioxide; Hydrogenotrophic methanogenesis; In-situ biogas upgrading; liquids; Membrane bioreactor; Methanobacterium; Methanoculleus; methanogens; partial pressure; Power to gas; sewage sludge; Sludge digestion
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.01.135

•Gas recirculation and H2 supply through a submerged membrane for in-situ upgrading.•94% H2 utilization efficiency was found at H2 flow rate of 0.87 L Lreactor−1 d−1.•CH4 production rate increased from 0.38 to 0.54 L Lreactor−1 d−1.•An increase of 42% in CH4 production was observed in the in-situ upgrading reactor.•Organic matter removal was not compromised despite the high pH level (8.1) In-situ upgrading of biogas in a mesophilic anaerobic digester of sewage sludge by sparging H2 through a membrane was studied. Large gas recirculation rates were required to facilitate H2 transfer to the bulk liquid phase; at  ∼200 L Lreactor−1 d−1, H2 utilization efficiency averaged 94% and the specific CH4 production increased from 0.38 L Lreactor−1 d−1, during conventional digestion, to 0.54 L Lreactor−1 d−1. Sludge digestion was not compromised by elevated H2 partial pressure nor by the associated rise in the pH (8.1) because of CO2 removal. In this regard, VFA accumulation was not detected and the performance of VS removal was similar to the observed without H2 supply. Microbial analysis revealed that homoacetogens were outcompeted by hydrogenotrophic methanogens. Methanoculleus sp., Methanospirillum sp., Methanolinea sp. and Methanobacterium sp. were the hydrogenotrophic archaea present over the experiment.