Publication: Attached benthic microalgae cultivation on flat sheet and tubular biofilm photobioreactor
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Date
2023-04-01
Authors
Siti Mariam Md Poad
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Abstract
Microalgae are currently in the spotlight due to its various potential such as feedstock food, livestock feed, fuel, fertilizers, fine chemicals and other value-added products. However, large cultivation of microalgae is not necessarily economically viable due to the high capital and operating cost. This leads to biofilm cultivation where the microalgae are grown on the surface of a porous substrate that ease the microalgae harvesting process and reduces water consumption and eventually the cost of cultivation. Thus, this study intended to study the cultivation of microalgae on the surface of the porous substrate. It comprises of four species of microalgae from benthic origin (Amphora coffeaformis, Cylindrotheca fusiformis, Navicula incerta and wild strain) and two types of flat sheet membrane as the porous substrate namely polyvinylidene fluoride (PVDF) and polyethersulfone (PES) and one tubular capillary PES membrane. Contact angle analysis revealed that PES membrane is more hydrophilic to PVDF membrane. For flat sheet membrane, the experiment was carried out on a glass plate covered with cellulose based absorbent paper in a glass chamber with medium circulation at 40.0 ml/min. Throughout 7 days of cultivation, highest areal biomass was achieved by PES membrane which at 16.26 ± 0.89 g DW/m2 for A. coffeaformis, 22.86 ± 1.05 g DW/m2 for C. fusiformis, 11.55 ± 1.95 g DW/m2 for N. incerta and 16.14 ± 2.76 g DW/m2 by wild strain. C. fusiformis achieved the highest areal biomass and biomass productivities on PES membrane compared to other species. This lead to the selection of PES material for porous substrate and C. fusiformis to be further studied on the tubular capillary porous substrate photobioreactor (PSBR). The experiments were carried out in a fabricated tubular column designed for microalgae cultivation with 0.5 ml/min medium circulation. The tubular capillary PSBR system C. fusiformis achieved areal biomass of 5.30 ± 0.34 g DW/m2 and is able to approach the biomass productivity of the conventional suspension culture.