BACKGROUND Remediation of wastewater using microalgae is an alternative way of reducing environmental impacts associated with wastewater treatment while simultaneously generating biomass that can be converted into biofuels. In this study, the phycoremediation of a secondary urban effluent by native microalgae was investigated using a photobioreactor designed to receive carbon dioxide (CO2). The experiments were carried out with and without CO2 addition, and the physicochemical parameters of the effluent were monitored. The biomass yield was determined as the dry weight, and both the lipid and fatty acid profiles were obtained by gas chromatography with mass spectrometry detection. RESULTS With respect to biomass production, lipid content and phycoremediation of the secondary urban effluent, the best results were observed in the experiments using CO2. In these experiments, reductions of biological oxygen demand (54.34%), total phosphorus (92.4%), ammoniacal nitrogen (97.1%) and total Kjeldahl nitrogen (92.8%) were observed. The CO2 addition also enhanced microalgae growth, as the maximum cell density (MCD) was 54.26% higher after a shorter period of time compared to the MCD obtained without CO2 addition. The biomass yields were 0.5324 +/- 0.007 g L-1 and 0.821 +/- 0.014 g L-1 without and with CO2 addition, respectively. The lipid yields per unit of biomass for the CO2 supplemented cultures were not statistically different from cultures that were not supplemented with CO2, and the same was observed for fatty acid composition. CONCLUSION The use of the mixed-type photobioreactor has been shown to be a potential alternative method for biomass production and wastewater phycoremediation. (c) 2019 Society of Chemical Industry