Phycodesalination Potential of <i>Graesiella emersonii</i> sp. NITD 23 Studied for Treating Synthetic Seawater, Industrial Wastewater, and Brackish Water

As the global demand for freshwater rises, reevaluating the state of existing desalination technologies is essential. Conventional techniques like reverse osmosis and multistage flash distillation are energy-intensive and costly. Phycodesalination, using microalgal/macroalgal cells to consume dissolved salts, offers an environmentally friendly alternative. This study examines the effectiveness of the indigenous algal strain Graesiella emersonii sp. NITD 23 in desalinating three simulated water samples: synthetic seawater [total dissolved solids (TDS)≈23,000 mg/L], synthetic industrial wastewater (TDS≈13,500 mg/L), and synthetic brackish water (TDS≈7,500 mg/L). Isolated from the saline coastal waters of the Andaman and Nicobar Islands and acclimatized under laboratory condition, G. emersonii sp. NITD 23 was assessed for biomass concentration and its impact on TDS, salinity, conductivity, and pH. The strain achieved maximum TDS removal of 27.16%±0.003%, 22.53%±0.006%, and 9.38%±0.002%, and salinity removal of 30.15%±0.010%, 26.75%±0.008%, and 29.79%±0.03% in synthetic seawater, industrial wastewater, and brackish water, respectively, at the end of 14 days. Biomass and chlorophyll content increased steadily, with a slight rise in pH observed at the end of the 14-day study. These findings indicate the halotolerance of the strain G. emersonii sp. NITD 23 and its potential as a pretreatment step to enhance conventional desalination methods, reducing energy consumption load.