State-of-the-art of R&D on seawater desalination technology

Fresh water deficit has been an increasingly critical global environmental issue, and seawater desalination is considered as the most effective and promising solution, which promotes the development of different desalination technologies. In order to provide a comprehensive knowledge about the development of desalination technologies, state-of-the-art of research and development on the application of desalination technologies is reviewed in this paper. At first, the overview of desalination technologies is briefly introduced, including the definition of desalination, the evaluation index of water quality and the resulting classification of water resources, the overview of desalination industry, the usages of freshwater produced by desalination, and the sources of raw water. Besides, conventional desalination methods are categorized into physical method and chemical method according to whether there is new substance generated in the desalination process. In the following section conventional desalination methods are reviewed from the perspectives of basic processes and principles, the performances and technical characteristics. However, the shortcomings of conventional desalination technologies mainly lie in high energy consumption and complex treatment process, such as the decrease of heat transfer coefficient caused by the scaling and fouling generated on the solid heat transfer walls for multi-stage flash (MSF) and multiple effect distillation (MED), and rigorous pre-treatment and low recovery factor for reverse osmosis (RO). With the aims of overcoming these disadvantages and thus decreasing the energy consumption, different improvements have been put forward and new desalination methods have been developed. Therefore, the development of desalination technology is then exhaustively analyzed and forecasted in the following four aspects: improvement for the existing technology, combination of different technologies, desalination technology in combination with new energy, and development of new desalination technologies utilizing unemployed physical phenomena. The improvements mainly focus on the shortcomings of MSF, MED and RO, which are the current major large-scale industrial desalination technologies. The combination of different technologies can integrate their respective advantages to improve the desalination performance and decrease the energy consumption and the cost. The limitations of the decrease of traditional fossil energy and its increasing cost can be broken through the combination with solar, wind, geothermal, ocean and nuclear energies, which is also regarded as a potential solution for climate change. The newly developed desalination technologies have the advantages of lower energy consumption and cost, but most of which are still in lab-scale and need further improvement. Due to the important role in the assessment of the desalination efficient, special attention is paid to the analysis of energy consumption of each desalination technology.