When considering one of the more popular desalination processes, reverse osmosis, practical water recovery in seawater desalination is hydraulically limited to approximately 60 percent, and in brackish water desalination, recovery is limited to approximately 80 percent by mineral scale formation. Restricted water recovery and increasing energy demand at higher recoveries might limit further improvement of currently used membrane desalination technologies. Distillation processes, and specifically membrane processes that utilize vapor pressure as a driving force, are not limited by the osmotic pressure of feed or brine streams, and might be a solution to overcome the limitations of current desalination processes.
Thus, the main objective of this research is to comprehensively investigate heat and mass transport in novel membrane distillation crystallization processes in which water is sustainably desalinated from supersaturated feed solutions and minerals can be simultaneously recovered for beneficial use.
The research focuses on measuring the rates of formation, size distribution, adhesion to membranes, and removal/harvesting of mineral crystals that form during desalination of water containing sparingly soluble salts. It also investigates the effects of operating conditions and environments on the sustainable production of purified water and minerals using the membrane distillation crystallization process. Controlled laboratory experiments will be carried out in which a rigorous scientific approach will be applied to identify, characterize, and quantify the individual and combined mechanisms controlling bulk and surface crystallization and their effects on heat and mass transport through the membrane. In particular, the focus of the research will be to identify the optimal operating conditions under which this hybrid desalination and mineral recovery process can be sustainably operated under supersaturated conditions to produce water and produce valuable mineral. Through the analytical methods and quantitative tools that will be developed as part of this research, improvements will be made to the current understanding of the fundamental principles and mechanisms involved in evaporation of water through scale layers followed by porous synthetic membranes. These will help the application of this knowledge in the modeling and design of small and large engineered systems.
Limited water recovery in existing desalination processes is the cause for elevated operating costs of desalination. This research will address the global need to increase water availability through the constant improvement of technologies that produce water at higher quality, lower energy demand, using renewable sources of energy, and without harming the environment. Understanding the mechanisms of reversible and repeatable membrane fouling scaling when treating supersaturated solutions by thermally driven membrane processes will mitigate one of the main problems encountered in desalination of saline water. Ultimately, the goal of this research is to improve our ability to provide clean water at an affordable cost to the public in modern and developing countries. The results will also facilitate the design of better treatment processes to reduce the discharge of brines to the environment and increase the reliance on natural resources, such as solar energy, for desalination. The research and educational plan will support the participation of undergraduate and graduate science and engineering students, and specifically from underrepresented groups/minorities in research and education. The development of interactive lecture and hands-on activities, and the establishment of continued education programs for pre-college teachers will enhance the interests of their students in science, engineering, and the environment, and will hopefully direct more motivated students to pursue higher education in environmental engineering.
