In this work, Spirulina platensis (SP.PL ) and mixed algal culture (M.X) were used as an economical treatment technology to solve dual environmental issues related to carbon dioxide (CO2) capturing and wastewater treatment. The impact of the concentration of CO2 (2.5%, 5%, 10%, and 15% v/v) on the specific growth rate (mu) of SP.PL and M.X, biomass production (P-x), carbon dioxide bio-fixation rate (R-CO2), organic matters and nutrient removals were assessed. The mu values of SP.PL and M.X increased by increasing the CO2 concentration until the optimum value (10v/v%) was reached, after that, increasing the CO2 dose negatively affected the growth rate. mu values ranged from 0.45-0.79 day(-1) for SP. PL and from 0.48 to 0.86 day(-1) for M.X. Both algae strains have shown high biomass productivities (P-x of 0.246 g(dw.)L(-1).d(-1) for SP.PL and 0.384g(dw.)L(-1).d(-1 )for MX), and significant carbon bio-fixation rates (R-CO2 of 0.360 g(c).L-1.d(-1) for SP.PL and 0.460 g(c).L (-1).d(-1) for M.M). the M.X obtained from the secondary basin of local WWTP performed better than single strain SP.PL in removing organic matter (% CODremoval 97.2), total inorganic nitrogen (% TIN(removal )99.6) and total phosphorus (T(Premoval)99.41) under all studied conditions. Microalgae with fast growth rate and naturally grown in the water system can be a sustainable and effective technology for CO2 uptake and nutrients removals. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.