What Is Reverse Osmosis?

Issues regarding freshwater production have persisted throughout human history. Several factors such as location, contaminants, temperature, salinity, dissolved solids, and others have hampered the distribution of clean water in many regions. Fortunately, the introduction of reverse osmosis has provided an efficient solution to this problem.

So what is reverse osmosis?

Reverse osmosis consists of the utilization of filtration systems which remove dissolved ions from water. Osmosis is an elemental force that draws water to water with higher salt content.

This is a process by which dissolved ions are removed from water. This elemental force can be surmounted by applied pressure with the usage of pumps and semi-permeable membranes, which forces water through the membrane and filters out dissolved salt from the water.

Reverse osmosis is a hot topic in the water treatment industry. With the lowest energy requirements, some of the highest recovery rates, and one of the best rejection rates on the market, it’s no wonder people are interested in learning more about it. What is the definition of reverse osmosis, though?

How does it work?

As anyone could guess, it is the process of osmosis backwards. Osmosis is the passage of water through a protein membrane (like our skin, or the inside of a plant cell) to equalize the concentration of particles dissolved in the water.

The protein membrane allows water to pass through, but molecules larger than water (things like minerals, salts, and bacteria) cannot. Water flows back and forth until the concentration is equal on both sides of the membrane, and an equilibrium is formed.

Let’s apply this knowledge to water purification. We want to drink water from a lake or stream, but it contains too high concentration of contaminants like salt, minerals, and bacteria, that make it undrinkable.

By applying pressure to water as it passes through a membrane, the water can be forced to move away from the membrane rather than attempting to form an equilibrium like normal.

This against-flow motion is where the “reverse” in “reverse osmosis” comes from. A pump works well for this process. Water is forced through the membrane, which like a super-fine particle filter, blocks an extreme majority of contaminants from coming through.