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Reverse Osmosis System in Water Purification: How it Works to Purify Water

Reverse Osmosis System

Before discussing the use of the reverse osmosis system in water purification, it is helpful to understand what osmosis is. Then we can discuss how reverse osmosis differs. It seems a fairly simple difference, yet reverse osmosis systems apply a form of technology that is against nature. It is not possible to use regular osmosis to remove impurities in your water supply.

To understand osmosis, you should understand what a semi-permeable membrane is. Here we shall explain the technology behind the system. This should make it easier for you understand the difference between reverse osmosis and other water purification methods.

What is Osmosis?

The term osmosis refers to the passage of a solvent from one side of a membrane to another. This process is known as diffusion. There are many examples of this in nature, particularly in how organisms control the passage of fluids, and the solids dissolved or dispersed in them, between body cells. A permeable membrane contains small holes that allows most dissolved and some particulate solids to pass through it.

Fundamentally, osmosis enables the passage of solvent and dissolved solids between two areas of different concentrations. It enables nature to create a balance between body cells of different solids contents. Nature likes a balance, and osmosis is its way of maintaining a balance. The term ‘semi-permeable’ refers to a membrane that does not allow all molecules to pass through, only those of certain dimensions.

How Does Osmosis Work?

Let’s consider a membrane separating two solutions. On side A of the membrane, there might be water containing a solution of 2% solids. On the other side, B may be a solution of 1%. Osmosis comes into play, and water from the 1% side will pass through the membrane to equalize the solids: so water passes from A to B until the solids content of each is 1.5%.

Once equilibrium has been reached between the concentration of dissolved salts or particles between each side of the membrane, then passage from high to low concentration stops. It is a form of filtration that permits only molecules of a certain size to pass through the membrane.

What is Reverse Osmosis?

What if you could reverse this process? Force water in higher concentrations of dissolved or particulate impurities back through a semi-permeable membrane into an area with low or zero concentrations of impurities? This would be sure to remove pure water from contaminated water. In fact, it is the principle behind the widely used reverse osmosis system in water purification.

So how does it work? On one side of the membrane (Side A) you have impure water and on the other (Side B) you have clean water. By applying pressure to Side A the water would be forced through the membrane into Side B – the clean side. The semi-permeable membrane can be designed to allow only molecules of a certain maximum size through. It is fundamentally a chemical filter that can remove substances that are larger than water molecules or substances of any other pre-determined molecular dimensions.

This process is known as ‘reverse osmosis’ because you are forcing water through the membrane rather than allowing the system to permit the more natural process to occur in the opposite direction. This process is used to remove unwanted particles and dissolved large molecules from your drinking water.

Reverse Osmosis System in Water Purification

In domestic reverse osmosis systems, the pressure is applied to water by an external source such as your household water pressure. This pressure forces pure water through the semi-permeable membrane, leaving the unwanted ions and large molecules behind.

It all seems very simple, but it is anything but! That said, reverse osmosis is a very effective method of water purification. It is widely used in domestic and commercial water purification systems worldwide.

See Also:  Best Reverse Osmosis Systems - Comparison and Buyer's Guide

Reverse Osmosis System – How an RO System Works to Purify Water

How does the reverse osmosis system work to purify water, and why should you use it? We will come back to that last question later, once you are more aware of how it works. First off, as explained above, reverse osmosis is not a natural process. It must therefore be applied correctly. Your system will go through the following steps when it purifies your water to make it safe to drink:

Initial Filtration: The water undergoes an initial filtration process. This filters out the solid particles through a sieve. It is important to filter out the larger particles of contamination before trying to pass them through the sensitive membrane. This could be silt, debris from the water pipes and any sediment that has been allowed through the municipal water system. Such sediment could harm the membrane.

Carbon Filter: A carbon filter is designed to remove certain contaminants that could harm the reverse osmosis membrane. Among these are chlorine and some others that can reduce the lifetime of the reverse osmosis membrane if not removed. The carbon adsorbs the contaminants onto its surface, just as activated carbon filters do.

Reverse Osmosis Membrane: This is the main working part of the reverse osmosis system in water purification. It allows water to pass through it but stops practically all dissolved solids and any small particles left after passing through the initial and carbon filtration processes.

Final Filtration: A good 4-stage reverse osmosis system will also include a final filtration unit. This generally consists of a carbon filter such as that described above. It may not be exactly the same type of filtration system, but it does provide backup filtration in the event of any extraneous contamination bypassing the process.

How Long Does a Reverse Osmosis System Last?

If you have a reverse osmosis water purification system and service it as recommended, it should last you at least 10 years. The semi-permeable membranes will occasionally need to be changed, and the whole system should be cleaned out at least annually. It might be necessary to do this more frequently if your water supply is particularly contaminated.

Reverse Osmosis System in Water Purification Summary

Reverse Osmosis is a form of water purification that can be used domestically. There are other ways of purifying your drinking water, although this is one of the more reliable techniques. We have explained how reverse osmosis works to purify your water, and why it is one of the best methods out there.

One important industrial use of the reverse osmosis system in water purification is the separation of pure water from seawater. It is significantly more effective than other techniques and is also very effective in purifying your domestic water supply. If you need pure water for your family, then this is an excellent choice as it also is if need purified water for industrial use.

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About the author

John Clark

John has been working in consumer appliances store for past 16 years. He is very passionate about his work and looking for various appliances reviews from his customers in those years. He loves to write well-researched articles on various home appliances.

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1 Comment

  • Hi John,

    This is a great post and addition to my post listed below. Thanks for sharing this detailed article about Reverse Osmosis.