Design And Optimization Of A Novel Bubble Column Photobioreactor And Its Integration With Raceway Pond

As the phototrophic growth of microalgae integrates high value compounds production, waste water treatment, carbon fixation and lipids accumulation, the research of photobioreactor (PBR) has attracted worldwide attention in recent years. In the present study, through the comparison of different kinds of cultivation system, the bubble column PBR demonstrated the best performance in cultivation and scale-up. Therefore, a series of optimization and scale-up were conducted to the bubble column PBR. As a result, a novel, scalable and high efficiency multi-column bubble PBR was developed. In addition, the multi-column bubble PBR was further integrated to a raceway pond to form an integration system which had many merits.Firstly, this study compared the performance of flat plat PBR and attached algae cultivation in labrotary scale. Before comparison, the flat plate PBR was optimized by installing inner structure (Type A), and the attached cultivation optimized by irradiation intensity, inoculation density and so on. The result shows that under indoor condition, the flat plate PBR has the better specific growth rate and productivity based on illuminated surface than the attached cultivation system. However, under outdoor condition, the bubble column PBR (70L) exhibited the highest specific growth rate ? (0.015 h-1) and productivity Pi of algae (0.6 g m-2 h-1), while the flat plate was intermediate (? was 0.014 h-1, Pi was 0.52 g m-2 h-1), and the attached cultivation was the worst (? was 0.006 h-1, P; was 0.19 g m-2 h-1).As the bubble column PBR had satisfactory algae cultivation performance, a novel closed multi-column bubble PBR was developed, which had the advantage of easy scalability, satisfactory light and mixing regime. In the assistant of CFD simulation, better aeration manner and aeration rate were demonstrated, and the diameter was also optimized. The cultivation experiment under outdoor condition with Chlorella pyrenoidosa exhibited high growth rate with 0.2 vvm and alternate aeration manner. And the optimized PBR showed obvious superiority over the prototype PBR, as the biomass concentration of optimized PBR reached 1.56 g L-1, which was 20.7% higher than that of prototype PBR.The traditional open and closed PBR have opposite advantages and disadvantages.In order to complement each other's advantages, an integrated system that combined raceway pond and multi-column bubble PBR was developed. This integrated system had better irradiation character and CO2 absorbing rate than traditional raceway pond, and heat that accumulated in closed column could rapidly release to open raceway pond, thus reduced the cost for cooling in summer weather. Under the optimized operation manner, the integrated system achieved 49% higher biomass concentration and productivity than that of control raceway pond.