Biohydrogen production using a granular sludge membrane bioreactor

•A high quality effluent was obtained and the granules were not disrupted.•Maximum hydrogen production was 475 mLH2 L−1 h−1 (OLR: 30 g L−1 d−1 and HRT: 4 h).•High OLR promoted a metabolic shift to solvent production.•Short HRT promoted the homoacetogenic metabolism.•Membrane fouling is affected by total EPS and the flux applied.