Another widely used configuration is the flat-plate PBR, which is constructed by employing slender rectangular containers composed of transparent material. These cylinders are tilted at certain angle, which allows maximum coverage of sunlight. Photoautotrophic cells cultivated in this PBR have high densities (>80 g/L). These are more appropriate for cultivation since they allow low accumulation of dissolved oxygen and allow photosynthesis to occur proficiently. Still, problems like tempera­ture control and adherence of algae to reactor walls exist.

13.3.2.2 Column Photobioreactors

This configuration of a photobioreactor offers the finest mixing, most manageable cultivation conditions and greatest volumetric mass relocation rates. They are eco­nomic and the setup is comparatively easy. Column PBR are aerated from the base and their translucent walls allow maximum exposure to light. They can also be illumi­nated internally.

13.3.2.3 Continuously Stirred Tank Reactors

The tank is in the shape of a broad, hollow, and capped cylindrical duct that has the potential to operate both outdoor and indoor. Risk of culture infection is extremely low. Stirring and illuminating apparatuses are inserted from above. Drainage systems and gas injectors are placed at the bottom and in the mid-section. The consistent turbulent flow induces algal growth and averts fouling of the culture.

When judged against the open pond systems, in a PBR the algal culture is efficiently protected from any sort of pollutant and loss due to low evaporation. The cultivation parameters (level of nutrients, temperature, pH level, etc.) can also be effectively managed.