Biomass production of Scenedesmus obliquus from mixtures of urban and olive-oil mill wastewaters used as culture medium

► Mixtures of wastewaters is a valid solution for optimization of microalgae cultures. ► OMW and UWST mixtures improved the Scenedesmus obliquus growth. ► The highest value of μm was determined when 25% (v/v) UWST added to 5% (v/v) BOMW. ► High carbohydrates and lipids contents have been determined in the biomass obtained. ► Final biomass can be used in biofuels production. The mixture of olive-oil mill wastewater (OMW) and urban wastewater from secondary treatment (UWST) as culture medium was studied. Experiments were performed in a batch bioreactor on laboratory scale, using Scenedesmus obliquus CCAP 276/3A. In this sense, two experimental series were prepared. In the first, the culture medium was formed by 0%, 1%, 2.5%, 5%, 10% (v/v) of OMW added to UWST. In the second, a constant proportion (5% v/v) of bleached OMW was maintained and 0, 10, 25, and 50 (v/v) of UWST were added. From the experimental results, the highest values of maximum specific growth rate (μm=0.074h−1), volumetric biomass productivity (Pb=4mgdm−3h−1), and net biomass generation (0.28gdm−3) were determined in the culture formed by 25% (v/v) of UWST added to 5% (v/v) bleached OMW. The final biomass was characterized by an accumulation of energy-rich compounds, such as lipids and carbohydrates which are capable of being transformed into biofuels.