Adel W. Almutairi
Aquaculture wastewater (AWW) contains elevated concentrations of nitrogen, phosphorus, and salts, in addition to many micropollutants that may cause environmental pollution if discharged untreated. This study evaluated the potential of the halophilic microalga Dunaliella salina for simultaneous phycoremediation of AWW and production of biodiesel-oriented biomass. Microalgal growth and biochemical composition were compared between AWW and synthetic f/2 medium under controlled laboratory conditions. Results showed that AWW supported efficient microalgal growth, showing a biomass yield of 1.32 g L−1 with a productivity of 0.09 g L−1 d−1, representing 40.88% and 18.42%, respectively, over that obtained in f/2 medium. Cultivation in wastewater also enhanced the volumetric productivity of lipids, proteins, and carbohydrates by 26.20%, 12.46%, and 26.38%, respectively. Significant nutrient removal from AWW was achieved, with high reduction efficiencies for nitrate, nitrite, ammonium, phosphate, and sulfate within the range 76.80–94.10%, along with a decrease in salinity by 29.70%. The lipid fraction was dominated by fatty acid methyl esters suitable for biodiesel production, representing 94.10% of the total lipids. Biodiesel properties met the international fuel standards and were even improved when the microalga was cultivated in AWW. These findings demonstrate that AWW can serve as an effective culture medium for halophilic microalgae, enabling simultaneous wastewater treatment and sustainable biofuel feedstock production.