Comparative Studies of Membrane Distillation and Reverse Osmosis for Seawater Desalination

Abstract

The essence of water in our everyday activities cannot be overemphasized. The major source of water in the Middle East is seawater and the most widely used technique for water treatment is Reverse osmosis (RO). However, the major challenge in the use of RO is the high-energy consumption resulting from the need for pumping at very high pressure. In this research work, the capability of a low-pressure Membrane Distillation (MD) technique as a replacement for RO was evaluated. A comparative study of MD and RO was done using process intensification, cost estimation, and process economic approach. The study was performed using process intensification metrics including mass intensity; waste intensity; productivity/size ratio; productivity/weight ratio; flexibility and modularity. The cost estimation involving the capital and operating expenses for RO and MD desalination plants was also determined based on the productivity of the plants. Moreover, process economic factors including profits, cash flow, and cumulative cash flow were also evaluated. The preliminary results obtained showed that the MD and RO possess the same capability to be used in the desalination plant based on process intensification. In addition, MD can be preferred in a situation where waste heat can be harnessed from neighboring industries. MD can also be better than RO with respect to the resistance of MD membrane materials to fouling. On the other hand, MD is more expensive than RO based on cost estimation and process economic results obtained.