| Membrane contactor processes are an emerging class of membrane separation processes that utilize concentrated brines or low grade heat sources to separate liquid streams and to enrich or strip gasses from aqueous solutions. Their low energy consumption and versatility of application make them an attractive alternative to pressure driven membrane processes.; Particular operating conditions and apparatus design determine the performance of membrane contactors. This work focused on developing a new approach to flux enhancement in membrane distillation (MD)—a membrane evaporation process and a member in the membrane contactor group. The effects of membrane module design, membrane selection, solution chemistry, and operating conditions have been shown to play a significant role in the mass and heat transfer in MD application for seawater desalination. Results have shown that with careful design of a direct contact MD (DCMD) apparatus, the flux is more than doubled compared to the best results published in the literature. Furthermore, a significant flux enhancement was achieved by using a novel configuration in which vacuum is induced on the permeate side of DCMD.; Other membrane contactor processes, like direct osmosis (DO), have found very specific applications in the food and beverage industry and recently in wastewater treatment applications. Combination of these processes alone or together with traditional pressure-driven membrane processes can further emphasize their advantages. In this work a combination of osmotic distillation (OD), another membrane evaporation process, and DO for pretreatment of wastewater before final treatment with RO have been studied for application in direct potable reuse of wastewater for long-term human space missions. Testing results indicate that the combined membrane contactors/RO process for wastewater reclamation is superior to competing technologies. The combined process provides high water recovery (>90%) at low energy consumption (<25 Wh/l), and with minimal resupply of consumables for its continuous operation.; Enhancement of mass transfer in membrane contactor processes and improving their apparatus design are crucial to making these processes more attractive for large-scale application. This will also initiate development of new and improved membranes specifically for these processes. |
