Enhancement of hydrogen production by optimization of biofilm growth in a photobioreactor

•Biofilm growth was monitored and controlled in real time.•Uneven distribution of biofilm in the photobioreactore was improved.•A loose biofilm structure with high hydrogen production activity was obtained.•Obtained a high Bio-hydrogen production concentration and production rate.

To improve biofilm activity and obtain a high hydrogen production performance of biofilm photobioreactor (BPBR), the biofilm growth on the fiber-optic surface was optimized by using a multi-sensor measurement system, plus biofilm thickness automatic control device. The proposed measurement system consisted of three types of sensors, i.e. biofilm thickness sensors, biomass concentration sensor and fiber Bragg grating temperature sensors, respectively, to monitor biofilm growth and distribution, cell adsorption/detachment rates, cell metabolic heat production and distribution in time-dependent tests. The biofilm thickness was controlled in real time using the designed biofilm control device and the information obtained from the biofilm sensors. The biofilm, in the improved BPBR, showed a loose structure and high hydrogen production activity. The H2 concentration and H2 production rate reached a high level of 45 μg/mL and 2.72 mmol/L/h, respectively, for the improved BPBR; these values were 1.73 times and 1.49 times those of the unimproved BPBR, respectively.