Cultivation of Oleaginous Microalgae Scenedesmus obliquus on Secondary Treated Municipal Wastewater as Growth Medium for Biodiesel Production

Local single cell microalgae isolated from a wastewater swamp and identified as Scenedesmus obliquus was used to determine its applicability for utilization of domestic wastewater for biomass and lipid production. Secondary treated domestic wastewater with or without mixing of growth medium was used to cultivate S. obliquus for the biomass and lipid production as a renewable feedstock for biodiesel. S. obliquus showed the highest OD when grown in 100% Bold's basal medium (BBM). S. obliquus utilized 95.2% and 78.5% of P and N contents, respectively, when grown in 25% WW+75% BBM mixture and the utilization efficiency of both elements decreased with the increasing wastewater portion in the mixture. Although the BBM displayed the highest dry biomass and lipid production (25.15% of the cell dry biomass). The lowest values were recorded for the uninoculated wastewater, followed by 100% wastewater enriched with S. obliquus. The obtained data revealed that the lipid classes of S. obliquus differs according to the cultivation medium and conditions. The highest percentage of C16-C18 fatty acids (54.76% from total lipids) were recorded in case of algae cultivated in 100% wastewater, followed by 46.96% in case of 100% BBM medium. These results suggest the utilization of mixtures containing a higher portion of secondary treated wastewater, such as 75% WW+25% BBM or 50% WW+50% BBM, could increase the economical production of the lipid-rich microalgae S. obliquus for biodiesel through saving water and nutrients.