Hydrogen production by Rhodopseudomonas palustris CQK 01 in a continuous photobioreactor with ultrasonic treatment

An ultrasonic treatment technique was applied to a continuous photobioreactor with Rhodopseudomonas palustris CQK 01 suspension to enhance photo-hydrogen production performance. After the start-up period, R. palustris CQK 01 suspension in the photobioreactor was intermittently agitated by ultrasonic wave with a frequency of 20 kHz and then the hydrogen production performance was evaluated. The ultrasonic agitation significantly dropped the hydrogen concentration in the suspension from 300 μmol/L to 50 μmol/L and thus increased the hydrogen production rate and hydrogen yield by nearly 2 times as compared with conventional photobioreactor. Furthermore, the effects of the ultrasonic power and time, influent substrate flow rate and concentration were investigated and discussed, respectively. The maximum hydrogen production performance of the continuous photobioreactor with ultrasonic treatment was obtained under the conditions of ultrasonic power 40 W, agitation/interval time 3/7 s, substrate concentration 75 mmol/L and substrate flow rate 40 ml/h, leading to the hydrogen production rate of 1.12 mmol/L/h and hydrogen yield of 0.23 mol-H2/mol-glucose.