Light filtration technology for sustainable microalgal biomass production

The use of native microalgal strains, which are well adapted to local environmental conditions, for sustainable biofuels production has largely been marred by photonics-related challenges. To date, most photobioreactor systems make use of artificial sources of illumination thus increasing the overall costs of biomass production. Solar energy, although sustainable and cost-effective, is difficult to manage and control. It also contains other wavelengths which are detrimental to microalgae. Thus, this study sought to make use of spectral filters for optimal outdoor algaculture. Hence, solar energy was used in wastewater-mediated algaculture of native and imported Chlorella sp. under blue, green, red and yellow coloured spectral filters. The native Chlorella sp. had the highest growth rate of 0.892 d(-1) and 0.754 d(-1) under green and blue coloured filters, respectively. In comparison, the imported Chlorella strain had a growth rate of 0.379 d(-1) and 0.267 d(-1) under green and blue filters, respectively. Both strains produced high lipid yields under the blue coloured filter, with the native and imported Chlorella strains managing lipid yields of 41.87% dry cell weight (dcw) and 32.29% dcw, respectively. The native Chlorella strain also significantly lowered (p < 0.05) the levels of total nitrogen and ammonium from wastewater with removal efficiencies of 92.17% and 44.60%, respectively, whereas the imported Chlorella strain managed a removal efficiency of 80.81% total nitrogen and 26.10% ammonium under the blue coloured filter. The results indicate that light filtration technology can be used, sustainably, in the simultaneous algaculture of native strains and remediation of wastewater.