چكيده به لاتين
In recent years, microalgae, considered as one of the promising renewable energy sources to substitute fossil fuels, which has been considered by many researchers. However, due to high processing costs, mass production of microalgae is not currently affordable. Microalgae cultivation as a surface attached biofilm is a novel method that can be an effective solution to reduce cultivation costs. In this study, a novel biofilm photobioreactor was made that can grow the biofilm in two ways: submerged in cultivation medium and also porous substrate or PSBR. A ceramic filter, was used as the cultivation substrate. Chlorella vulgaris in BG-11 medium was used for experimental evaluation of the photobioreactor. In continuous and intermittent submerged culture, photobioreactor did not perform well, but in cultivation in the form of porous substrate, microalgae were able to grow well on the substrate. The biofilm was also simply harvested through scraping from the surface of the ceramic substrate by using a spatula and the ceramic filter can be reused for a long time and for reculture. Based on the experimental results, optimum parameters were obtained for 17000 lux light intensity, 7 days harvest time and 14 mL/day medium flow rate. It was found that the aeration rate did not have a significant effect on the biofilm growth rate. Also, in this study, a new method based on the use of digital photographs of the biofilm surface was used to determine the dry weight. Comparison of the results obtained from digital photographs with experimental data, confirms the accuracy of this method in estimating the dry weight. The thickness of biofilm formed in the culture of the porous substrate was in the range of 73.13-328.51 µm. The moisture content of the produced biofilm was 79.823±7.244 which shows significant reduction in energy consumption and dewatering costs. Furthermore, experimental results showed that applying 0.6 bar vacuum to the ceramic substrate can reduce the moisture content of the harvested biofilm by more than 20%. Comparing the results obtained in this study with other biofilm photobioreactors demonstrates the proper performance of the designed photobioreactor.
