Removal of nutrients from salt-rich wastewater via freshwater microalga Tetradesmus obliquus

In this study, freshwater microalga ( Tetradesmus obliquus GEEL-11) was cultured in municipal wastewater supplemented with various NaCl concentrations (0–150 mM). The microalgal growth kinetics, morphological changes, nutrient removals, salinity change, fatty acids (FAs) composition, and biodiesel quality were investigated. Maximum microalgal growth was observed upon 75 mM salt addition, while the increase in salt hindered the growth of T. obliquus GEEL-11. T. obliquus GEEL-11 exhibited high nutrient removal N (87–99%) and P (94–100%) from municipal wastewater under various salt stress. The cell size of T. obliquus GEEL-11 increased and intracellular vesicular structures proliferated. The salinity dramatically decreased, indicating that T. obliquus GEEL-11 might be able to remediate saline wastewater. The palmitic acid (C16:0) and stearic acid (C18:0) accounted for 28.90–34.02% and 43.61–62.09% of T. obliquus GEEL-11, respectively. T. obliquus GEEL-11 exhibited significant quantities of fatty acids, representing its potential for biodiesel production. This study demonstrated that T. obliquus GEEL-11 could effectively remove N and P from wastewater embedded with high salt concentrations for biomass production.