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Reverse Osmosis water treatment has been commercially available and proven since the 1960's. However, while the core process remains the same, only Pure Home RO™ has developed patent pending improvements resulting in the "next generation" RO products affordable for home and commercial applications.
To understand "reverse osmosis," it is probably best to start with normal osmosis. According to Merriam-Webster's Collegiate Dictionary, osmosis is the "movement of a solvent through a semi-permeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane." That's a mouthful. To understand what it means, this picture is helpful:
On the left is a beaker filled with water, and a tube has been half-submerged in the water. As you would expect, the water level in the tube is the same as the water level in the beaker. In the middle figure, the end of the tube has been sealed with a "semi-permeable membrane" and the tube has been half-filled with contaminated water (in this case a salty solution) and submerged. Initially, the level of the contaminated solution and the pure water are equal, but over time, something unexpected happens -- the water in the tube actually rises. The rise is attributed to "osmotic pressure."
A semi-permeable membrane is a membrane that will pass some atoms or molecules but not others. In the figure above, the membrane allows passage of water molecules but not other molecules (in this example, salt). One way to understand osmotic pressure would be to think of the water molecules on both sides of the membrane. They are in constant motion. On the salty side, some of the pores get plugged with salt atoms, but on the pure-water side that does not happen. Therefore, more water passes from the pure-water side to the salty side, as there are more pores on the pure-water side for the water molecules to pass through. The water on the salty side rises until one of two things occurs:
- The salt concentration becomes the same on both sides of the membrane (which isn't going to happen in this case since there is pure water on one side and salty water on the other).
- The water pressure rises as the height of the column of salty water rises, until it is equal to the osmotic pressure. At that point, osmosis will stop.
In reverse osmosis, the idea is to use the membrane to act like an extremely fine filter to create drinkable water from contaminated water. The bad water is put on one side of the membrane and pressure is applied to stop, and then reverse, the osmotic process. The result is clean, pure water!
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