Reverse Osmosis Filtration: The Basics

iStock_000003615521MediumReverse osmosis (RO) is one of several processes that enables the removal of salt from seawater, rendering it potentially fit for human use. It is a popular method utilized in recycling and wastewater treatment, as well as consumer water filtration systems. It was back in the 1950s that scientists first considered the use of RO to desalinate ocean water, and although it worked, it was not practical due to the small volume produced. This changed when two UCLA scientists created hand-cast membranes made from cellular acetate, allowing larger quantities of water to move through the RO process more efficiently. In 1965, the first commercial RO desalination plant began running a small scale operation in Coalinga, California.

Reverse Osmosis Explained

Osmosis, without the reversal part of the equation, is when a solvent of low concentrated solute solution moves through a membrane to get to the higher concentrated solution, thus weakening it. To explain the process of RO, let’s start with a saltwater solution on one side of a tank and pure water on the other side, separated by a semi-permeable membrane. Pressure is applied to the saltwater side of the tank, counteracting the natural osmotic pressure from the pure water side, thereby pushing the saltwater through the filter. Due to the size of the salt molecules, only the smaller water molecules make it to the other side, thereby adding fresh water to the water side, and leaving the salt on the other side.

The best water filter system is one that removes all the harmful particulates while remineralizing the water

A Few Fascinating Facts about Reverse Osmosis

  • The production of maple syrup uses RO to separate the sugary concentrate from water in the sap.
  • The dairy industry uses RO filtration to concentrate whey and milk.
  • Wastewater goes through the RO process to create something drinkable, thereby earning the nickname, “toilet to tap” which may be unappealing, but provides developing nations with the ability to produce drinkable water.

Reverse Osmosis Consumer Water Filtration Systems

Consumer RO filtration systems generally do a good job of stripping out harmful contaminants, chemicals, minerals, and salt, but in the process, also strip the water of essential minerals. There is some disagreement on this issue, with some health experts stating that the amount of minerals in water is negligible anyway, so RO systems are a great option. However, the venerable World Health Organization and many other health experts have stated that water is an important source of minerals such as calcium, magnesium, and iron, especially for people in developing countries. The best water filter system is one that removes all the harmful particulates while remineralizing the water. That assures that it not only tastes great, but has the health benefits that essential minerals provide.


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