Direct brackish water desalination using Chlorella vulgaris microalgae

Abstract

The objective of this study was to investigate the suitability of direct use of Chlorella vulgaris for brackish water desalination as a new conceptual technique. First, the adaptation of Chlorella vulgaris in saline water was performed, and then the living microalgae cells were utilized for the desalination process using a bubble column photobioreactor. The effect of culture medium, time, salinity and initial inoculum on the microalgae growth and salinity removal was investigated and the optimum conditions were obtained by RSM−CCD method. To assure the consumption of sodium chloride (NaCl) content of water by microalgae, the BG11 culture medium was modified by substituting its chloride and sodium containing salts by nitrate, calcium and potassium containing minerals. The results indicated that the enhancement of microalgae growth and salt removal efficiency were more pronounced in the modified-BG11 (MBG11) culture medium. Using Chlorella vulgaris microalgae in the MBG11 culture medium, the decrease in brackish water electrical conductivity for different NaCl concentrations between 1000 and 5000 ppm, was between 80 % and 40 %, respectively. Atomic absorption and flame photometry analyses confirm the hypothesis of adsorption of Na+ ions on the Chlorella vulgaris cell surface. © 2020 Institution of Chemical Engineers