Recently, the Union Environment Ministry had issued a draft notification that seeks to regulate membrane-based water filtration systems in areas where the source of water meets drinking water norms of the Bureau of Indian Standards. This primarily affects reverse osmosis (RO)-based water filtration systems and the rules effectively prohibit homes from installing domestic RO systems. Brief in short, what is Reverse Osmosis? What is the problem with Reverse Osmosis? Explain.

Answer: RO was originally a technology devised to desalinate sea water. The idea exploits the principle of osmosis. Take a tube, twist it into a ‘U’-shape and insert a semi-permeable membrane (a material with very small holes that will allow only certain molecules to filter through) at the point where the tube curves. Fill half the tube with salt water and the other with freshwater. Over time, fresh water will cross over into the salty arm until the proportion of salt and water in both arms is the same. This is due to osmotic pressure which dilutes a ....