Performance of immobilized microalgal strains for biodesalination of real seawater

In this study, biodesalination was performed using four different microalgal strains (Euglena deses, Chlamydomonas reinhardtii, Trichormus variabilis, and Scenedesmus obliquus) in real seawater for the first time in immobilized method. Immobilized beads in the ratio of 1:1, 1:2, and 1:3 (biomass to sodium alginate), were applied directly to real seawater in nutrient-deprivation conditions. The chloride ion reduction was measured for 15 days continuously. The other parameters investigated were pH, chlorophyll, absolute cell count, and oxygen microsensor. For Cl⁻ ion, the highest elimination capacity on day 15 was measured to 18.1 g.m⁻³.hr⁻¹ for C. reinhardtii (1:1), the highest among all the studied strains and ratios. Among all the strains, the highest chlorophyll content of 234 ± 0.43 mg·L⁻¹ was measured for Trichormus variabilis (1:1) on the 15th day, and cell leaching was measured by flow cytometer analysis with ∼6.14 × 10⁸ cells·mL⁻¹ were released from the beads. In oxygen microsensor tests, oxygen content decreased as depth was increased, indicating that growth occurred closer to the surface. Immobilization increased algae's salt tolerance capacity, resulting in the prolonged cellular life span. Biomass harvesting is not required if the algae can be consumed in the immobilization technique. The performance of biodesalination using an immobilized treatment method with more efficient salt-removing microalgal strain is recommended.