The PPR NIRON system by NUPI Industrie Italiane has been used for a reverse osmosis water treatment station to serve the co-generation system of a plastics processing plant. Osmosis refers to the extension of a liquid that passes through a semipermeable membrane from the compartment with greater water potential (lower concentration of solute) towards the compartment with lower water potential, in synthesis we pass from a lower concentration of solute to a greater one. In the reverse osmosis process, on the other hand, pressure is applied to the "container" where the water is less pure to overcome its natural tendency, thus reversing the natural osmotic flow. The advantage over other methods of water treatment is that the reverse osmosis, in addition to removing the dissolved salts, also retains bacteria, germs, particles and dissolved organic substances. The reverse osmosis then succeeds in completely eliminating the polluting particles of size up to one ten thousandth of a micron, as well as pesticides, pyrogens, viruses and bacteria, thus ensuring the absolute bacteriological purity of the water. It has been estimated that reverse osmosis can retain 90 to 99.9% of the substances dissolved in water. This is why it has become the most widely used filtration technology at industrial level, from the biomedical to the food industry, to the treatment of industrial wastewater and to the generation of drinking water from the sea. Reverse osmosis is a process of separating foreign bodies from water by using semipermeable membranes. The membranes allow the passage of water but retain the dissolved mineral elements, colloids and bacteria. The water to be treated is pushed into the membrane by a pump, which exerts a pressure higher than the osmotic one, so as to obtain two outgoing flows: the part of incoming water that passes through the membrane constitutes the permeate (poor of salts) that can be used, while the remaining part comes out with a high salt concentration, due to the accumulation of all the salts that have not crossed the membrane. This is the concentrate (rich in salts) that should be discarded. The advantages obtained from the use of the reverse osmosis treatment system are substantial cost savings, improved energy efficiency, constant permeated water quality, enhanced overall system performance, 24-hours of uninterrupted purified water, maintenance reduced to a minimum.