Effect of optical panel distance in a photobioreactor for nutrient removal and cultivation of microalgae

The aim of present investigation is to assess the effect of illumination area and distance of an optical panel (OP) on the growth of microalgae with simultaneous removal of nutrients. Four different distances of OPs were used i.e. 225 mm OP (Run 1), 150 mm OP (Run 2), 112.5 mm OP (Run 3) and 90 mm distance OP (Run 4) in the photobioreactor (PBR) operations. The PBR was equipped with an OP and operated with a total volume of 37-l. A batch culture was prepared using an initial cell concentration of 1.12 ± 0.05 g l−1. The experiments were conducted at neutral pH (7.2 ± 0.3) under dark and light cycles of 8 and 16 h, respectively. The diffuse light intensity was recorded as 91, 93, 95 and 98 % for Run 1, Run 2, Run 3 and Run 4, respectively, at a 300 mm depth level in the PBR. The chlorophyll content per cell was found to be an average of 701, 721, 785 and 808 fg for Run 1, Run 2, Run 3 and Run 4, respectively. High chlorophyll content per cell and diffuse light intensity was observed for Run 4 compared to other fractions. However, Run 3 sample possessed approximately 10.51 % higher biomass growth along with 15.22 % chemical oxygen demand, 18.15 % total nitrogen 2.37 % NH4-N, 15.1 % total phosphorus and 15.05 % PO4-P more removal than the Run 1. These findings suggest that in terms of economic consideration and efficiency of nutrients removal, Run 3 is found to be more effective than other samples. Moreover, an enhanced growth of Chlorella vulgaris could further be utilized as a potential biodiesel source.