Reverse Osmosis - what is it?

The process of reverse osmosis for water treatment was developed almost half a century ago. It was first developed for the desalination of seawater. On recognizing the potential for decontamination, the commercialization of reverse osmosis filtering systems was initiated for the purpose of domestic water purification. Systems based on reverse osmosis were introduced into homes in the early 1970s. It was believed to be a real alternative to the expensive and wasteful distillation units.

The Reverse Osmosis Process Explained

The process of reverse osmosis is based on forcing water at high pressure through a membrane which is semi-permeable. Reverse osmosis is quite simply the opposite of the natural process of water osmosis. Osmosis is the behavior of water when it migrates from a weak saline solution to a stronger one, which gradually equalizes the saline composition of both solutions when they are divided by the membrane. Reverse osmosis requires the process to be done in reverse, as its name suggests. Water is forced to migrate from the stronger saline solution to the weaker one, passing through the membrane. Due to the fact that salt molecules have a larger physical size than water molecules the salt molecules are blocked by the membrane. The use of the membrane results in the division of desalinated water, and a concentrated saline solution, at the end of the process. A certain quantity of contaminants found in drinking water are also eliminated during the process, and because of this, reverse osmosis has been put forward as a method for efficiently purifying drinking water.

The Good …

Reverse osmosis water purification is an important process in obtaining mineral-free water as an end product. The typical mineral constituents in water are bigger than the water molecules themselves. Therefore, they can be caught and stopped in the membrane and eliminated from water when a reverse osmosis filtering process is used. Typical minerals include calcium, iron, lead, salt and manganese. Reverse osmosis can remove certain chemical elements of drinking water as well, including fluoride.

… And The Not So Good

However, even though the reverse osmosis process can extract various contaminants in drinking water, its filtering abilities are not perfectly matched with the challenges of filtering water that has been municipally treated – which is what the general population receives. Municipal water includes contaminants such as chlorine and volatile organic chemicals. These contaminants are of a smaller physical size than water molecules, and therefore they cannot be stopped from passing through the filtering membrane with the water. The end result is that they remain in the drinking water.

In addition, the reverse osmosis process produces acidic water; because it removes the natural alkaline mineral constituents found in water. Acidic water is dangerous for the body, causing teeth and bones to be lose calcium and other essential minerals so as to neutralize the water’s acidity level. Water has always had some elements of minerals and their elimination by filtration results in unhealthy drinking water.

Although the reverse osmosis process tends to be less wasteful than the distillation process, it is still incredibly inefficient. An average of three gallons of water is wasted in order to produce one gallon of purified water.