How does an RO system work ?

All RO systems, whether domestic or commercial, work on the same principle, namely the principle of Reverse Osmosis. There may be some add on’s as well depending on the system one buys eg. RO with TDS controller or RO + UV etc. But all in all, the purification is done through the RO process.

The best way to understand reverse osmosis is to first understand the natural process of osmosis. Osmosis is said to occur when a solvent flows from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.

Quite a mouthful isn’t it ! Let me simplify it for you.

Think of it like this. You have a glass which is divided into 2 regions. One region has highly concentrated salt water and the other region has plain water. If you place a semi-permeable membrane (in this case, a membrane which allows only water molecules to pass through and not salt molecules) in between these 2 regions, water will flow from the plain water region to the salt water region, to equalize the water concentration on both sides. This happens automatically without the application of any external energy.

The reason why this happens is because of the 2nd law of thermodynamics. In case you are interested to read further, I encourage you check this out :

http://en.wikipedia.org/wiki/Second_law_of_thermodynamics

Now when the water starts moving from one region to another through the membrane, it places some pressure on it. Just like when you use a sieve when pouring tea to catch the tea leaves, the sieve feels some pressure because of the tea moving through it. This pressure felt on the membrane during osmosis is called osmotic pressure.

In Reverse osmosis, we reverse this process. So, from salty water, we try and take out as much soft water as possible. The result is a small quantity of soft water and a larger quantity of even more salty water (called waste water). We achieve this by using a pressure pump and applying pressure on the membrane which is higher than the osmotic pressure. This way the water is forced through the membrane, which traps other particles and allows only water to pass through.

Think of the pump as the heart of the RO system and the membrane as the mind. The pump forces water through the membrane at high pressure to extract soft water from the hard water. The waste water which you get from an RO system, is not actually waste in the literal sense. It’s just water from which a quantity of soft water has been taken out leaving the remaining water even harder than before.

This is the basic principle of how an RO system works. Feel free to leave any question that you might have in the comments section and i’ll answer them to the best of my ability.