Reverse Osmosis was developed as a water treatment method more than 40 years ago. The process first arose as a technique of desalinating seawater. Once the method’s decontaminating capabilities were recognized, reverse osmosis systems began to be commercially produced for home water purification purposes. Such systems were installed in homes as early as the 1970s. Reverse osmosis systems seemed a viable option to the more costly and energy-wasteful distillation units. The application of reverse osmosis to the solution of problems in water treatment requires an understanding of the basic mechanisms involved in the process, the limitations of reverse osmosis and the pre-treatment requirements.