Cultivation of microalgae in wastewater is a promising and cost-effective approach for both CO biofixation and wastewater remediation. In this study, a new strain of Coelastrum sp. was isolated from cattle manure leachate. The isolated microalgae were then cultivated in wastewater. Effects of different sCOD concentrations (600, 750, 900, 1050 mg L) and light intensities (1000, 2300, 4600, 6900 and 10000 Lux) on biomass production, CO consumption rate and nutrient removal from wastewater were investigated. The results showed that maximum cell growth and CO consumption rate were 2.71 g L and 53.12 mg L day, respectively, which were obtained in the wastewater with 750 mg L sCOD and under the light intensity of 6900 Lux. The microalgae were able to completely consume all CO after incubation period of 4 days. The highest sCOD, total Kjeldahl nitrogen (TKN), nitrate and total phosphorous (TP) removal at such conditions were 53.45, 91.18, 87.51 and 100%, respectively. The lipid content of microalgal biomass was also measured under different light intensities; maximum amount of lipid was determined to be 50.77% under illumination of 2300 Lux. Finally, the CO consumption rate and biomass productivity of microalgae in semi-batch culture with continuous gas flow (CO 6%:N 94%) were investigated. The rate of CO consumption and biomass productivity were 0.528 and 0.281 g L day, respectively. The TKN, nitrate, TP and sCOD removal rate of microalgae were 83.51, 80.91, 100, 41.4%, respectively.

Microalgae cultivation is a promising approach to remove ambient CO via photosynthesis process. This paper investigates the impact of high CO concentrations (6, 12, and 16%) on algae growth, CO biofixation, lipid and carbohydrate contents, and nutrient removal of newly isolated microalgae, Coelastrum sp. SM. In addition, the ability of microalgae to produce biodiesel at optimal condition was studied. The microalgae were cultivated in wastewater using an airlift photobioreactor. Under 12% CO, the maximum biomass productivity and CO fixation rate were 0.267 g L day and 0.302 g L h, respectively. Total Kjeldahl nitrogen (TKN), total phosphorous (TP), nitrate, and sCOD removal efficiency were 84.01, 100, 86.811, and 73.084%, respectively. Under 12% CO and at the same condition for cell growth, the highest lipid and carbohydrate contents were 3 7.91 and 58.45%, respectively. The composition of fatty acids methyl ester (FAME) of the microalga lipid was defined. Based on the obtained results and FAME profile, Coelastrum sp. SM was a suitable feedstock for biodiesel production and also, the organism had a great potential for CO biofixation, which is also more suitable than any other reported strains in other related studies.

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