How Does a Reverse Osmosis System Work?
A reverse osmosis system (RO) is a water purification system that uses a semi-permeable membrane to remove contaminants and sediment from your drinking water. This semi-permeable membrane has microscopic pores that allow water molecules to pass through, but block ions, unwanted molecules and larger particles from entering the water.
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Reverse Osmosis works with the same basic osmosis process that occurs naturally in nature: As molecules pass through a semi-permeable membrane, they leave the more concentrated side of the membrane and move on to the less concentrated side until their concentration is balanced. This is also called osmotic pressure.
The higher the osmotic pressure, the more concentrated the solution becomes until both sides reach the same concentration. This is what happens when a solvent of a low-concentrated solution moves through a semi-permeable membrane into a higher-concentrated solution until the two solutions reach equilibrium.
For example, if you’re sitting in a room surrounded by sugary syrup, water on one side of the arm wants to find balance with pure water on the other side of the arm. So water from the contaminated side moves through the membrane into the less-concentrated side of the arm, weakening the sugary concentration.
This osmosis process is important in many industrial processes, such as distilling rainwater collected from storm drains or boiling boiler water at power plants to control corrosion and increase efficiency. In the wine industry, for example, reverse osmosis has been used to concentrate sugary grape juice into clear liquids and to remove impurities such as acetaldehyde.
A RO system usually includes four stages of filtration: a sediment filter, a pre-carbon block, a reverse osmosis membrane and a post-carbon filter. The first two filters, the sediment and pre-carbon blocks, filter large particles from the water. The second two, the reverse osmosis and post-carbon filters, filter dissolved contaminants such as ions and heavy metals, like lead.
There are many types of filters that you can use for a RO system. A sediment filter removes dirt, sand and other particles down to 5 microns. A pre-carbon block filter uses activated carbon to attract and bond with positively charged ions in the water, such as chlorine and chloramines.
Another type of filter used for a RO system is a thin film composite membrane. These membranes have a high rejection rate of 95-98% and are more durable than cellulose triacetate membranes. They are prone to damage from chlorine, so they must be protected with a carbon filter before they can be used in a RO system.
Adding a permeate pump to an RO system is the best way to increase its efficiency and reuse the wastewater from the membranes. A permeate pump can reduce the wastewater from an RO system by 75 to 80%.
Reverse osmosis systems can help eliminate the need for bottled water by producing high-quality drinking water right in your home. They are available for the whole house or individual use and produce a constant supply of clean, filtered water to keep your family healthy and well-hydrated.