WateReuse - 2010 Desalination by Reverse Osmosis: How it Began and Where it Is Now

摘要

INTRODUCTION TO THE REVERSE OSMOSIS PROCESS How did Reverse Osmosis (RO) technology get started? Let's begin with a close look into osmosis. One of the most interesting and fascinating natural phenomena, osmosis is the basis for the fastest growing desalination technology called Reverse Osmosis (RO). Natural osmosis governs how waters transfer between solutions with different concentrations. It is also the basis for the way in which human skin and organs function, and how flora and fauna maintain a water balance. Due to the nature of the RO process it cannot be characterized as a filtration process or as treatment. As in natural osmosis, water tends to flow from a solution with a lower concentration to a solution with a higher concentration. As shown on Fig. 1,where there is a semi-permeable barrier such as a membrane, when pressure is applied to a concentrated solution that exceeds osmotic pressure, clean water will be displaced out of the concentrated solution while salts will remain in the concentrated solution. Theoretically, salts should not pass through the membrane, but in practice we observe salt leakages as a result of the diffusion, despite the fact that membrane "openings" are much larger than the molecules of water (H_2O) and many other ions in the water that may pass through the membrane.