Simultaneous coproduction of hydrogen and methane from sugary wastewater by an “ACSTRH–UASBMet” system

• A two-phase “ACSTRH–UASBMet” system was established in this study.
• The optimum HRT of acidogenic and methanogenic reactor was determined.
• Total energy recovery and conversion rate of substrate were calculated.
• Sugary wastewater was promising for hydrogen and methane coproduction.

A two-phase “ACSTRH–UASBMet” system has been investigated at the stepwise decreased HRT for the simultaneous production of hydrogen and methane in this study. Hydrogen could be continuously produced from the two-phase hydrogen fermentation of sugary wastewater in ACSTR and effluents from hydrogen fermentation were converted into methane in UASB reactor. At optimum conditions (HRTH: 5 h, HRTMet: 15 h), the highest hydrogen production rate of 5.69 (±0.06) mmol L−1 h−1 was obtained from sugary wastewater and methane was continuously produced from effluents of hydrogen fermentation with a production rate of 3.74 (±0.13) mmol L−1 h−1. The total bioenergy recovery by coproduction of hydrogen and methane from sugary wastewater reached 19.37 W and a total of 92.41% of substrate was converted to the biogas (hydrogen and methane) with two-phase anaerobic fermentation.