Continuous hydrogen production using upflow anaerobic sludge blanket reactors: effect of organic loading rate on microbial dynamics and H 2 metabolism

BACKGROUND Enriching hydrogen ( H 2 )‐producing bacteria by suppressing methane‐ producing microorganisms is a critical step in continuous biological H 2 production. Selective inhibition of methanogens can be achieved by varying the organic loading rate ( OLR ) in continuous reactors. In this study, continuous H 2 production was examined using mixed anaerobic cultures fed glucose in upflow anaerobic sludge blanket reactors ( UASBRs ) operating at 37°C and at pH 5.0 by varying the OLR at a constant hydraulic retention time. RESULTS A stable H 2 yield of 1.64 ± 0.04 mol mol −1 glucose was obtained at OLRs from 8.6 to 12.8 g COD L −1 d −1 . Increasing the OLR increased the hydrogenase flux and suppressed methanogenesis. At high OLRs , high acetate and solvent production were associated with Clostridiaceae and Ruminococcaceae while at low OLRs , the presence of Synergistaceae and Propionibacteriaceae were related to the production of propionate and other reduced byproducts. CONCLUSION This study successfully demonstrated continuous H 2 production using bench‐scale UASBRs fed glucose. Understanding the OLR effect on H 2 production and microbial interaction is important in the full‐scale operation of H 2 production facilities using low value feedstocks such as switch grass, corn stover and shorghum. © 2016 Society of Chemical Industry