Algae-Based Approach for Desalination: An Emerging Energy-Passive and Environmentally Friendly Desalination Technology

Desalination processes are critical for producing freshwater from salty water, and an algae-based desalination approach has drawn increasing attention as a potential low-cost and passive-energy desalination technology, which could be a competitive solution to desalination in remote areas impacted by water shortages. As the first comprehensive review in this emerging research field, a systematic analysis of the published results from the relevant studies is presented, and algae salt removal mechanisms are summarized. It is suggested that both nonmetabolic biosorption and metabolic-dependent bioaccumulation make contributions to salt removal, but bioaccumulation had a relatively minor role and required a significantly longer time for the reaction compared to the biosorption process. To select the most appropriate algae species for an algae-based desalination process, salt acclimation and salt removal abilities are considered as the two key selection criteria. Process configuration, influent water characteristics, algae harvesting, and reuse should also be taken into consideration during algae screening and selection. Based on the advantages and limitations of an algae-based desalination system, we have suggested different implementation strategies for algae-based desalination systems. Utilization of algae for brackish water treatment could be a more viable option compared to the seawater desalination. Combining an algae-based desalination system with wastewater treatment or the RO process could potentially improve the overall system economic feasibility. The focus areas of future studies are recommended, including system life-cycle cost analysis, energy efficient separation of algae from the effluent, mathematical simulation of the salt removal process, and the effects of engineering approaches on the salt removal process.