You have probably heard the term reverse osmosis, and may even have had reverse osmosis filtered water. Most of us have reaped the benefits of reverse osmosis, even if we haven’t realized it. Reverse osmosis is used to remove contaminants from tap water, manufacture fruit juice concentrates, keep water from spotting on your car in a car wash, and even used to grow the food we eat.
But what is reverse osmosis exactly? How does reverse osmosis work? These questions have complicated answers that require gaining a better understanding of the natural process of osmosis to fully grasp. Before investing in a reverse osmosis filtration system for your home or business, it is helpful to understand what reverse osmosis is, how it works, and what the advantages and disadvantages of these systems are.
Reverse osmosis is a process that is commonly used to remove contaminants, particulates, and other solid material from a water source. Reverse osmosis is a man-made process, unlike osmosis which occurs naturally.
Reverse osmosis was first developed over two and a half centuries ago in France by Jean-Antoine Nollet, a member of the French clergy and a physicist. Over the subsequent two centuries, other scientists began to implement the reverse osmosis process in their laboratories.
The use of reverse osmosis remained isolated to laboratories until 1950 when the University of California Los Angeles began using the process in a desalination plant. The use of reverse osmosis to desalinate seawater opened the doors for the use of reverse osmosis across a wide variety of industrial and commercial applications.
Reverse osmosis, as the name implies, is the reverse of the natural process, osmosis. To gain a good understanding of how reverse osmosis works, it is necessary to first understand how osmosis works.
Osmosis is a naturally occurring process that is necessary for life as we know it. Osmosis has a couple of moving parts that you should understand, as they will be important during a discussion of reverse osmosis.
At a basic level, osmosis is the movement of a fluid across a semipermeable membrane from an area with a low concentration of solute to an area with a high concentration of a solute.
Let’s break down what these terms mean:
During osmosis, the solvent moves through the semipermeable membrane from an area with a low solute count, referred to as a hypotonic solution, to an area with a high concentration of solute, known as a hypertonic solution. This movement of the solvent across a membrane from a low concentration solution to a high concentration solution may sound odd, is easily illustrated if we look at a plant.
Plants acquire their nutrients and water through the process of osmosis. The plant’s roots go down into the soil and spread out. In the process of osmosis, the plant’s roots are the semipermeable membrane. The soil is the hypotonic solution or the solution with a low concentration of solute. The plant roots are the hypertonic solution, or the solution with the high concentration of solutes. Water is the solvent, while nutrients necessary for the plant to sustain life are the solute.
Water carrying nutrients moves from the area with a low concentration of nutrients (soil), across the semipermeable membrane (the roots), to the area with a high concentration of nutrients (the plant itself).
Osmosis isn’t confined to plants. It is a driving force behind life as we know it, and plays an important role in how the human body functions. Osmosis is the process through which our bodies maintain normal levels of salt and other minerals.
Osmosis is even the fundamental process underlying kidney dialysis, a common medical treatment. One problem that many patients who have chronic kidney failure have is a buildup of fluids. Kidney dialysis uses osmosis to remove this excess water. In kidney dialysis, the dialyzer membrane functions as the semipermeable membrane. On one side is an artificial solution that is high in sugar, while on the other side is the patient’s blood. The membrane in the middle won’t let the sugar pass through the membrane, while the extra water in the patient’s blood is diffused across the membrane into the area with a high concentration of sugar.
Now that we have a firm understanding of how osmosis works, we can begin to answer the question, “how does a reverse osmosis system work?”. Reverse osmosis flips the normal process of osmosis but retains the same concepts.
Reverse osmosis is the process where a solvent moves across a semipermeable barrier from a solution with a high concentration of solute, or a hypertonic solution, to a solution with a low concentration of solute, or a hypotonic solution, using pressure.
Remember that osmosis occurs naturally, utilizing what is known as osmotic pressure to facilitate the movement of a solvent across the membrane. Reverse osmosis systems involve the unnatural movement of a solvent across a membrane from a high solute solution to a low solute solution, so the pressure required to cause that movement must be externally provided.
Perhaps the easiest way to illustrate reverse osmosis in practice is desalination. Desalination is the process of removing salt from seawater to create freshwater. Water, the solvent, is forced across a membrane using hydrostatic pressure. The solution on one side is seawater, which is rich in salt. So, seawater functions as the hypertonic solution. Water is able to move across the membrane, but the salt molecules are too large to move across as well, leaving them behind. The result on the other side is freshwater with a low concentration of salt, making it a hypotonic solution.
The example of seawater highlights the importance of the semipermeable membrane in the reverse osmosis process. If you have ever wondered, “how does a reverse osmosis filter work?”, the answer here lies in the size of the molecules that it allows to pass to the other side. In a desalination plant, the filter membrane allows smaller molecules like water to pass through, while larger molecules like salt are too big to pass through the membrane.
Reverse osmosis is used primarily to remove contaminants from water, but it also has a wide variety of other uses. Although the solvent involved in reverse osmosis is most commonly water, other liquids and even gasses can undergo the reverse osmosis filtration process to remove unwanted particles and molecules.
Here are some of the top uses of reverse osmosis today:
While reverse osmosis is a crucial process for many commercial and industrial applications and is increasingly relied on for cost-efficient residential drinking water, there are some downsides worth touching on.
The first downside is that reverse osmosis is sometimes seen as too effective at filtration by removing all of those dissolved solids from water. Reverse osmosis water has reduced mineral content. In certain parts of the world, such as developing countries, these minerals can provide a health benefit.
In developed countries like the United States, the vast majority of people get their required minerals from their diet, so this is less of a concern.
Reverse osmosis is the process where a solvent, typically water, is pushed across a membrane using externally provided pressure to remove contaminants, particles, and other molecules that are too large to fit through the membrane. Desalination, or the process of turning seawater into freshwater, is a prime example of reverse osmosis.
Reverse osmosis is not a natural process but is rather the reversal of the natural process of osmosis. Reverse osmosis requires some external force to increase the pressure of a solution to pass across a membrane that will remove unwanted molecules and dissolved solids.
Reverse osmosis is a highly effective filtration process for removing dissolved solids from water. Reverse osmosis removes not only minerals and salts from water, but it can remove bacteria, fluoride, and other dissolved solids that other filtration methods don’t. This makes it an ideal method for producing potable water in both a commercial and residential setting.
To learn more about residential reverse osmosis drinking water systems, please contact Rayne today. We have locations in both Arizona and California! Everything from reverse osmosis systems in Phoenix to water softeners in San Diego! Check out the location nearest you!