Municipal wastewater utilization for biomass and biodiesel production by Scenedesmus obliquus HM103382 and Micractinium reisseri JN169781

Municipal wastewater is a major problem due to its high concentration of nutrients, which can cause eutrophication of the surrounding water, resulting in serious disturbance in health and ecosystem. Microalgae can utilize nitrogen and phosphorus in wastewater as a potential source of cost effective and sustainable means for biodiesel production. Two microalgal species including Scenedesmus obliquus HM103382 and Micractinium reisseri JN169781 were cultivated in domestic wastewater (influent and effluent) that was pretreated and supplemented with 15% CO₂ in order to accomplish simultaneous nutrient removal and lipid production from wastewater. The biomass yield and lipid production were relatively high using either autoclaved or filter-sterilized wastewater compared to using either UV-irradiated or unsterilized wastewater (control). M. reisseri and S. obliquus grown in the autoclaved influent showed high biomass yield (0.41 ± 0.01 and 0.26 ± 0.03 g dry wt. l^-1) and lipid content (22% and 19%), respectively. The highest removal rates of nitrogen (97%), phosphorus (98%), and inorganic carbon (77%) were achieved by M. reisseri cultivated in the autoclaved influent. The saturated fatty acids fractions accounted for 66% and 60% of the total fatty acids accumulated in M. reisseri grown in the filter-sterilized influent and the autoclaved effluent, respectively, which is desirable for good quality biodiesel.