Operational Optimization of 1000L Flat Panel Photobioreactor for Economical Mass Production of Halophilic Microalgal Strain Pseudanabaena limnetica (Lemm.) Komárek

Microalgae have been widely used in industrial applications around the world for centuries, but large-scale cultivation of algae in photobioreactor (PBR) is still facing many challenges in terms of cost of construction, system size, culture sustainability, and productivity. The production of algal feedstock is hindered by the inability to translate laboratory studies into field scaleups. This chapter focuses on the research conducted for the construction of a low-cost flat panel PBR system and optimisation of its operational strategies. The microalgal strain chosen for mass cultivation is the indigenous halophilic species, Pseudanabaena limnetica (Lemm.) Komárek, which can withstand high temperature and high light intensity in summer season and can be grown in seawater. Therefore, real seawater has been used in this research study of cost-effective biomass production. Three scales of airlift panels have been developed for the flat panel PBR system, ranging from 8L up to 250L. The dimensions of the airlift panels are as follows: 1st : 25 cm x 38 cm x 10 cm (8L), 2nd : 50 cm x 70 cm x 20 cm (60L), 3rd : 100 cm x 110 cm x 28 cm (250L). A study was conducted to optimize the air flow rate and the size of the sparger pore for adequate aeration (CO2) and agitation. Physical parameters like, Sparger velocity (v) m/s along with change in Reynolds number (Re), superficial velocity of gas (Usg), gas holdup was studied for their efficiency to support algal growth. Also, optimization of other important parameters like light intensity, inoculum size was carried out in laboratory condition and correlated with the biomass production. Each PBR was operated outdoors after optimization. Electric power consumption was also discussed along with its cost estimation and total biomass productivity as well as the operational feasibility of the PBR systems developed. After optimizing the operational strategy for the working of PBRs in lab and outdoor conditions, it was found that 60L flat panel was the most suitable for large-scale cultivation of P. limnetica. Therefore, attempts have been made to construct and assemble 1000L PBR using 60L PBR units in outdoor conditions.