Cultivation of <i>Synechococcus</i> HS-9 in a novel rectangular bubble column photobioreactor with horizontal baffle

As a source for third-generation biofuel, microalgae can assist island countries to overcome their energy crisis. In this study, a novel photobioreactor having three segments is designed and Synechococcus HS-9 growth in the photobioreactors with and without a baffle is compared. The aims of this study are to investigate how the baffle influences bubble size, distribution, and velocity, to explain the bubble coalescence phenomena, and verify the effect of the baffle on Synechococcus HS-9 growth. The results showed that bubble size distribution in the photobioreactors paralleled the increasing air flow rate. At a flow rate of 1.0 L/min, most bubbles had a diameter of 200-400 mu m; however, at 2.5 L/min, the typical size was 1400-2000 mu m. Bubble velocity was observed through imaging techniques. The intake air flow rate of 1 LPM has a mass transfer coefficient value of 0.00075 m/s for the photobioreactor without the baffle and 0.00089 m/s for the baffle-bearing photobioreactor. The Sauter mean diameters at three different heights (A, B and C section) in the photobioreactors were 675 mu m, 1001 mu m, and 1125 mu m. Synechococcus HS-9 growth was 2.17 times higher in the baffle-bearing photobioreactor than that in the photobioreactor without the baffle.