Effect of thermal pre-treatment on inoculum sludge to enhance bio-hydrogen production from alkali hydrolysed rice straw in a mesophilic anaerobic baffled reactor

The effect of thermal pre-treatment on inoculum sludge for continuous H-2 production from alkali hydrolysed rice straw using anaerobic baffled reactor (ABR) was investigated. Two reactors, ABR(1) and ABR(2), were inoculated with untreated and thermally pre-treated sludge, respectively. Both reactors were operated in parallel at a constant hydraulic retention time of 20 h and organic loading rate ranged from 0.5 to 2.16gCOD/Ld. The results obtained indicated that ABR(2) achieved a better hydrogen conversion rate and hydrogen yield as compared with ABR(1). The hydrogen conversion rates were 30% and 24%, while the hydrogen yields were 1.19 and 0.97mol H-2/mol glucose for ABR(2) and ABR(1), respectively. Similar trend was observed for chemical oxygen demand (COD) and carbohydrate removal, where ABR(2) provided a removal efficiency of 53 +/- 2.3% for COD and 46 +/- 2% for carbohydrate. The microbial community analysis using 16S rRNA phylogeny revealed the presence of different species of bacteria, namely Clostridium, Prevotella, Paludibacter, Ensifer, and Petrimonas within the reactors. Volatile fatty acids generated from ABR(1) and ABR(2) were mainly in the form of acetate and butyrate and a relatively low fraction of propionate was detected in ABR(1). Based on these results, thermal pre-treatment of inoculum sludge is preferable for hydrogen production from hydrolysed rice straw.