If you just start to do algae culture in PBR, dont try to make it in a big size of reactor. Light and Mixing are very important parameter when you design PBR.
You start with designing the column (Dia. Height, sparger, liquid height, air flow, irradiance density, light cycle). Then you need to consider the algae in column, after that, you should consider the measurement techniques. All the above recommendations of design should base on the selection of the type of the PBS.