Cultivation of newly isolated microalgae Coelastrum sp. in wastewater for simultaneous CO2 fixation, lipid production and wastewater treatment.

Cultivation of microalgae in wastewater is a promising and cost-effective approach for both CO2 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-1) and light intensities (1000, 2300, 4600, 6900 and 10000 Lux) on biomass production, CO2 consumption rate and nutrient removal from wastewater were investigated. The results showed that maximum cell growth and CO2 consumption rate were 2.71 g L-1 and 53.12 mg L-1 day-1, respectively, which were obtained in the wastewater with 750 mg L-1 sCOD and under the light intensity of 6900 Lux. The microalgae were able to completely consume all CO2 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 CO2 consumption rate and biomass productivity of microalgae in semi-batch culture with continuous gas flow (CO2 6%:N2 94%) were investigated. The rate of CO2 consumption and biomass productivity were 0.528 and 0.281 g L-1 day-1, respectively. The TKN, nitrate, TP and sCOD removal rate of microalgae were 83.51, 80.91, 100, 41.4%, respectively.