Biohydrogen production by Chlorella vulgaris and Scenedesmus obliquus immobilized cultivated in artificial wastewater under different light quality

The algal biotechnology together with the wastewater treatment can contribute to the production of renewable energies such as bioethanol, biodiesel and biohydrogen and solve many of the challenges currently facing the shortage of fossil fuels and environmental impacts. Hydrogen as the cleanest source of energy is a promising alternative to conventional fossil fuels. Among different technologies for hydrogen production, photosynthetic microorganism, such as microalgae, has a great potential to produce hydrogen, by using only water and sunlight. One of the great opportunities is that microalgae can be cultivated in urban wastewater, which contains sources of carbon and nutrients, helping to reduce the cost of biomass and energy production. Microalgae C. vulgaris and S. obliquus immobilized grown in urban wastewater was proposed for the production of biohydrogen by sulfur deprivation and two light quality prior to anaerobic condition at pH 7.5 and 30 °C and 140 µE/m²/s of light intensity. The results indicate that blue light induces greater algal growth than under Purple light, while the maximum hydrogen production was for cultures under purple light of 128 mL H₂/L (productivity 204.8 mL H₂/L/day) and 60.4 mL H₂/L (productivity 39.18 mL H₂/L/day) for S. obliquus and C. vulgaris, respectively. An additional advantage is the high removal of organic carbon by S. obliquus cultures under purple incident light compared to C. vulgaris, being a double benefit; energy production and wastewater treatment.