Hydrogen and methane bio-production and microbial community dynamics in a multi-phase anaerobic reactor treating saline industrial wastewater

•Techno-economic feasibility of biogas production from saline effluent was studied.•Immobilized sludge anaerobic baffled reactor and salt-adapted culture were employed.•Temperature and OLR changes affected salt-tolerant bacterial/archaeal communities.•H2/CH4 yield increased at low OLR and 35 °C under high salinity (15–25 gNaCl/L).•Multivariable analysis showed the importance of OLR, temperature and configuration.