Biohydrogen production performance in a draft tube bioreactor with immobilized cell

The research was carried out using a draft tube fluidized bed bioreactor (DTFBR) system with immobilized cell. The total working volume of the DTFBR including the buffer tank and pipe was 2.4 L. The pH, volatile suspended solid (VSS) and total solid (TS) concentrations of the seed sludge were 6.8, 33.3 and 65.1 g/L, respectively. The thermally treated sludge was used for immobilization. Immobilization of cell was essentially achieved by silicone gel (SC) entrapment approaches. The entrapped-cell system operated stably at a low HRT without any cell washout. Hence, the H2 production rate was enhanced via increasing organic loading rates. The system was fed with sucrose-based synthetic medium, and was examined for its H2 production performance under different influent sucrose concentrations, different solid volume volumetric content and hydraulic retention times. found that the optimal solid volume volumetric content was 7.5% (v/v) when the solid volume volumetric contents ranged from 5 to 15% in the DTFBR. The maximum H2 production rate of 2.59 H2 L/h/L with H2 volumetric content of 36.8% and sucrose conversion of 80.5% was obtained at initial substrate concentration of 20 g COD/L, 7.5% (v/v) of solid volume, and HRT 0.5 h. The features of well mixing, high H2-producing performance and stable operation imply that using DTFBR system is a feasible approach to continuous H2 production in reality.