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[Infographic] How Does Reverse Osmosis Work?

How Reverse Osmosis Works: The Basics

Let’s take a look at exactly how the reverse osmosis works.

This type of water purification involves removing 99.9% of contaminants from unfiltered water to be left with nothing more than fresh, filtered water.

The unfiltered water is forced through a semi-permeable membrane, which has small pores that trap dissolved solids like salt, stopping them from passing through. Water molecules are small enough to pass through the pores, so only clean water makes it out of the other side.

The impurities that are left over are sent straight down the drain, leaving only delicious, pure drinking water.

The best RO filtering systems push water through a number of different filters and membranes for optimal results. Because not all contaminants are the same size, this helps to remove as many different types of impurities through a combination of filtration steps.

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How Does Reverse Osmosis Work? A Detailed Example

Let’s make things a little clearer with a simple example of how the reverse osmosis process works. Imagine we have a water solution that contains a significant salt concentration.

The salt particles are what we need to remove to make the water drinkable and clean. In scientific terms, the water is referred to as the “solvent”, and the salt is referred to as the “solute”.

The only way to separate this salt from the water, in the case of reverse osmosis, is to use a semi-permeable membrane.

This membrane sits directly between two water storage units, and consists of thousands of tiny holes that are just big enough to allow the water to pass through, but block the salt from making it to the other side. In this way, the water and the salt are separated, leaving the water that passes through salt-free and safe to drink.

During reverse osmosis, while the water that’s left over begins to get pretty crowded with salt, more and more pure water will be forced from this side over to the clean water side, leaving a high concentration of the solute on one side, and only the solvent on the other side.

Enough pressure needs to be applied to counteract the osmotic pressure from the side containing pure water, so that reverse osmosis can effectively separate water from unwanted particles at a fairly efficient rate.

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