Reverse osmosis (RO) is a method of water deionization or demineralisation that employs a semi-permeable membrane and pressure. The water undergoes removal of ions and minerals.
Osmosis
Understanding reverse osmosis requires familiarity with natural osmosis
Osmosis is a significant natural process that occurs spontaneously. Salt is transported from a solution with lower concentration to one with higher concentration in this process. Osmosis is a natural process observed in plants, where roots absorb water from the soil, and in humans, where the kidneys remove excess fluid. You need to read the below points carefully for properly understanding this process now.
The phenomenon of osmosis can result in the alteration of colour
For a membrane to be classified as semi-permeable, it must selectively allow certain atoms or molecules to permeate while impeding the passage of others. A screen door provides a straightforward example. Objects larger than the dimensions of the screen door’s apertures cannot pass through, while those smaller in size are able to. Gore-tex is a commonly used material in outerwear. The material is a thin plastic layer containing numerous microscopic holes. Water vapour can permeate pores, whereas liquid water cannot due to their minuscule size.
Reverse osmosis is the term used for the process of osmosis in reverse. Now reverse osmosis requires external energy input to the more saline fluid, whereas osmosis occurs spontaneously without such intervention. Reverse osmosis employs a semi-permeable membrane that selectively permits the passage of water molecules, while impeding the majority of dissolved salts, organic compounds, bacteria, and pyrogens. Reverse osmosis membrane is utilised to desalinate water by applying pressure greater than the osmotic pressure of the source water. The pure water will pass through while the contaminants are contained.
- Under high pressure, pollutants are separated from water molecules by a semi-permeable barrier.
- Colour Reverse osmosis is a process that involves the use of a semi-permeable membrane to remove impurities from water
A high-pressure pump is necessary to pressurise the salt side of the RO system, facilitating the flow of water through the semipermeable membrane. The outcome is a reject stream containing approximately 95-99% of the dissolved salts. The salinity of the feed water is a crucial factor in determining the required pressure. A higher concentration of feed water is desirable as it necessitates greater pressure to counteract osmotic pressure.
The reject stream refers to the water flow that contains concentrated impurities that did not pass through the RO membrane. On the other hand, the permeate water is the desalinated water that has undergone further treatment to remove any remaining minerals or ions.
Reverse osmosis membranes
Pressurised feed water enters the RO membrane, enabling water molecules to permeate while salts and other impurities are expelled through the reject stream. The reject stream can be either discharged or recycled back into the feed water supply to conserve water. Permeate or product water refers to the water that successfully passes through the RO membrane. The water’s dissolved salt content has undergone a reduction of approximately 95-99%.
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