An economic and environmentally friendly approach for sustainable wastewater treatment, CO2 abatement, and resource recovery via assimilation into biomass would be — Phycoremediation. Thus an attempt was made to investigate the effect of CO2 gas supplement on an ozone pre-treated tannery effluent (OPTE) accustomed microalgae Nannochloropsis oculata, Chlorella vulgaris, and Chlorella sorokiniana for their nutrient removal efficiency, biomass productivity, CO2 fixing rate, lipid content, and fatty acid composition in OPTE. The experiments were conducted in a glass reactor maintained at optimized cultivation conditions within the algal chamber. In which, the CO2 gas was supplied intermittently through a glass tube immersed in the reactor. Among the species studied, C.sorokiniana has revealed its better performance towards nutrient removal i.e. NH4+-N (96%) and o-PO43− (100%) with the maximum biomass yield and CO2 fixation rate of 2.1 ± 0.15 g/L and 0.48 g CO2/ L/d respectively. While the results recommended the N. oculata for biodiesel production owing to its maximum lipid accumulation potential (51%) and lipid yield (703 ± 2.8 mg/L). Further, the predicted biodiesel properties of N. oculata were good associations with the standard biodiesel quality. Thus, the phycoremediation of OPTE with the supplement of CO2 can be considered as a sustainable treatment method owing to the recovery of value-added biomass for biodiesel production. © 2021 Elsevier B.V.