Using wastewater to grow algae is probably the most promising route to reduce production costs associated with nutrients and water. In this study, a newly isolated facultative heterotrophic freshwater microalgae strain, Auxenochlorella protothecoides UMN280, was examined for algal growth, wastewater nutrient removal efficiency, and lipid accumulation in batch and semi-continuous cultivation with various hydraulic retention time using concentrated municipal wastewater (CMW) as cultivation media. The results of the 6 day batch cultivation showed that the maximal removal efficiencies for total nitrogen, total phosphorus, chemical oxygen demand (COD) and total organic carbon (TOC) were over 59%, 81%, 88% and 96%, respectively, with high growth rate (0.490 d(-1)), high biomass productivity (269 mg L-1 d(-1)) and high lipid productivity (78 mg L-1 d(-1)). Further fatty acid methyl ester (FAME) analysis showed that the microalgal lipids were mainly composed of C16/C18 fatty acids (accounting for over 94% of total fatty acid), which are suitable for high-quality biodiesel production. The system could be scaled up from 100 mL flasks to 25 L BIOCOIL reactors, and semi-continuously operated at hydraulic retention time of 3 days with a net biomass productivity of 1.51 g L-1 d(-1) of dried algae. (c) 2012 Elsevier Ltd. All rights reserved.