Sustainable biorefinery associated with wastewater treatment of Cr (III) using a native microalgae consortium

Microalgae have emerged as renewable and sustainable candidates for biorefineries since they can generate bioproducts and bioenergy through the removal of contaminants contained in wastewater. In the present study, a native microalgae consortium (NMC) is isolated from a wastewater treatment plant, and used to remove 100 mgL⁻¹ Cr(III). The native microalgae consortium is enriched in a photobioreactor with the following conditions: Bold's Basal Medium (BBM), pH 8, room temperature and 20 µmolm⁻²s⁻¹ light intensity. The molecular characterization reveals the presence of the following species: Tetradesmus sp., Scenedesmus sp and Ascomycota sp. The development of microalgae is evaluated through the production of biomass, pH, protein, lipid and carbohydrate, while the consortium presents the potential to obtain biofuels. The ability of the consortium to absorb two different sources of Cr (III) was determined using real tannery wastewater and synthetic water prepared with Cr₂(SO₄)₃. The adsorption efficiency of the microalgae is analyzed using adsorption isotherms of Langmuir model, indicating 99% adsorption efficiency of 100 mgL⁻¹ Cr(III). FT-IR and SEM analyses enable to identify the presence of Cr(III) in the native microalgae consortium. The promising features of this NMC underpin the idea of establishing a sustainable biorefinery to generate different bioproducts, in order to achieve a resource-efficient biomass use for a circular bioeconomy.