Integrated Membrane Distillation and Bubble Column Dehumidifier – A New Energy-efficient Solar-powered Water Desalination System

Water desalination using Membrane Distillation (MD) is an emerging thermal-membrane separation technology that has a potential to compete with conventional desalination processes. MD process is very attractive due its lower operating temperatures (from 50 to 90C) and pressure (close to atmospheric pressure), high salt rejection, compactness, low cost, less fouling problems, and currently considered of high distilled productivity. The current proposal aims at developing an energy-efficient (low-cost and low energy consumption) air sweeping multistage MD module integrated with bubble column (BC) dehumidifier for water desalination powered by solar energy. A New device (and process) for water desalination in which MD module is used to separate water vapor from the saline feed solution, and an integrated bubble column dehumidifier to condense the permeated vapor, in a closed cycle, and in a compact design are proposed. The system is based on an innovative design of integrated multistage MD and bubble column dehumidification. The innovation of the proposed system is mainly in the design of the multistage MD module and the process of condensation as a benefit of the integrated system, where the energy required for collecting the vapor (permeate) from the MD module, cooling the module, and condensing the vapor (product, distilled water) is focused and cycled. The BC dehumidifier has very high effectiveness and is used to condense the permeate vapor and cool the air before sending it back to the MD module for collecting the vapor. The energy required for the condensation and cooling is greatly minimized for the proposed integrated system due to the low thermal conductivity of the air and high effectiveness (usually above 95%) of BC dehumidifier. Our objective is to develop a compact model unit of our design and prove its effectiveness in producing low-cost desalinated water. It is also the objective to study scaling up the device for commercial use in future as an in-house local industry.