Recovering hydrogen production performance of upflow anaerobic sludge blanket reactor (UASBR) fed with galactose via repeated heat treatment strategy

•Repeated heat treatment improved hydrogen production performance by 37%.•Proteobacteria and Bacteroidetes population were significantly affected.•Clostridium populations was identified as the dominant microflora.

This study evaluated the effect of repeated heat treatment towards the enhancement of hydrogen fermentation from galactose in an upflow anaerobic sludge blanket reactor with the hydraulic retention time of 6 h and the operation temperature of 37 °C. The hydrogen production rate (HPR) and hydrogen yield (HY) gradually increased up to 9.1 L/L/d and 1.1 mol/mol galactose, respectively, until the 33rd day of operation. When heat treatment at 80 °C for 30 min was applied, hydrogen production performance was enhanced by 37% with the enrichment of hydrogen producing bacteria population. The HPR and HY were achieved at 12.5 L/L/d and 1.5 mol/mol hexose, respectively, during further 30 cycles of reactor operation. The repeated heat treatment would be a viable strategy to warrant reliable continuous hydrogen production using mixed culture.

Graphical abstractEnhancement of hydrogen fermentation from galactose in a continuous upflow anaerobic sludge blanket reactor (UASBR) at 80 °C for 30 min (Day 33) during repeated heat treatment with a hydraulic retention time (HRT) of 6 h. The heat-treatment resulted in the increased hydrogen production performance by 37% and the enrichment of hydrogen producing bacteria population.Download high-res image (154KB)Download full-size image