What is Reverse Osmosis?Source: Wikipedia
Reverse osmosis (RO) is a membrane-technology filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side.
How Reverse Osmosis Works
In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (High Water Potential), through a membrane, to an area of high solute concentration (Low Water Potential). The movement of a pure solvent to equalize solute concentrations on each side of a membrane generates osmotic pressure. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications. However, there are key differences between reverse osmosis and filtration. The predominant removal mechanism in membrane filtration is straining, or size exclusion, so the process can theoretically achieve perfect exclusion of particles regardless of operational parameters such as influent pressure and concentration.
Reverse osmosis, however, involves a diffusive mechanism so that separation efficiency is dependent on solute concentration, pressure, and water flux rate. Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other substances from the water molecules.
The efficiency of a reverse osmosis water filter is affected by the water pressure coming into the system and the temperature of that water. Membranes are tested at 65 psi of pressure and temperature of 77 degrees. For each incremental change in either variable, membrane performance changes accordingly. Higher pressures increase production and vice versa. The optimal pressure is 65 PSI and temperature is 77°, as seen here on our reverse osmosis pressure/temperature chart.
What are the Stages in a Reverse Osmosis System?
Below is a simplified and exploded diagram of a typical 4-stage reverse osmosis system. The stages have been numbered and the arrows show the directional flow of the water as it moves through the system. A larger diagram of the membrane is featured at the bottom to show its many layers, the component of the system that makes it a ‘reverse osmosis’ system.
Melt Blown Polypropylene removes dirt, rust and sediment particles down to 5 microns. There are several different types of sediment cartridges.
Pleated filters feature increased surface area and longer life. These cartridges are washable and reusable.
Melt blown polypropylene filters are designed for the removal of dirt, rust and sediment from water. 5 and 20 micron are the most popular sizes for drinking water applications.
String wound filters are an inexpensive solution to your filtration needs. These cartridges come in a variety of media types and have a wide range of applications.
Coconut Shell Carbon Block Cartridge(s), 10 Micron removes chlorine, taste, odor and chemical contaminants.
Activated carbon block filters typically have a 0.5 to 10 micron filtration capability, making it also helpful for particulate filtration, removing taste and odor from chlorine, insoluble lead reduction, and demonstrating, in some cases, removal of Giardia and Cryptosporidium. A 5-stage reverse osmosis system has an third housing to hold an additional carbon block cartridge.
Thin Film Composite (TFC) rejects (removes) 95% of Total Dissolved Solids (TDS) down to .0001 Microns.
Thin film composite membranes (TFC or TFM) are semi permeable membranes manufactured principally for use in water purification or water desalination systems. They also have use in chemical applications such as batteries and fuel cells.
Coconut Shell Activated Carbon is the final polishing filter after storage tank, just before you use the water.
Inline post filters typically clip onto the top of a reverse osmosis system’s membrane housing. The post filter removes any chlorine or contaminants missed by the other cartridges or membrane.
What Can Reverse Osmosis Remove From Drinking Water?
The reverse osmosis process can remove a myriad of organic and inorganic contaminants from your tap water.
These systems specialize in removing chlorine taste and odor, rust, sediment and also alleviate common worries about public water by reducing or completely removing arsenic, asbestos, chromium, fluoride, lead, mercury, VOCs, THMs, giardia and cryptosporidium. For a more expansive list, view our contaminants removed by reverse osmosis list or our thin-film membrane particle size removal chart above.
What Makes Up a Reverse Osmosis System?
The following components make up your reverse osmosis system:
Pre-filter #2 (And #3 If Applicable)10 Micron Carbon Block removes chlorine and chemical contaminants in the feed water and protects the RO membrane.
- Instructions for Quick-Connect Fittings.
Our Reverse Osmosis Systems
Hydraulic fracturing (sometimes referred to as fracking or hydrofracking) is a relatively new form of natural gas extraction.
The fluids used in the fracking process flow back to the surface, often entering the water table or polluting the drilling area, and sometimes improper disposal of waste water from the wells.
As our technology advances, so do new forms of pollution and contaminants that effect our environment and our health.
Read more about drinking water contaminants and their health effects.
Chlorine has long been recognized as an oxidative agent, meaning that it not only kills the germs in the water supply; it will damage any living tissue with which it comes in contact. And your skin, like the rest of your organs, is living tissue. But that’s not the only problem.
Since the discovery of its health benefits in the mid-1940’s, fluoride is often added to the public water supplies of industrialized countries in order to reduce the populations tooth decay, which is especially effective in low income communities, where good dental hygiene may be too costly.
Chromium-6 was found in the drinking water supply of the southern California town of Hinkley and brought to national attention by Erin Brockovich.
The EPA is reviewing effects of Chromium-6 after a recent report brought to light dangerous levels in a number of major US cities.
Giardia is a flagellated protozoan parasite that colonizes and reproduces in the small intestines of humans and other animals, which can cause giardiasis.
Symptoms of Giardiasis usually show after 3 to 4 days, and include gastrointestinal and constitutional problems.
Cryptosporidiosis is a disease caused by the parasite Cryptosporidium parvum.
Since a outbreak in 1993 in Wisconson, new attention has been focused on determining and reducing the risk for Cryptosporidiosis from community and municipal water supplies.
What is ultraviolet light? Do I need to filter the water before the UV process? How exactly can light kill organisms?
Visit our ‘How Ultraviolet Purification Works‘ guide to find out how it works.
The typical water softener is a mechanical appliance that’s plumbed into your home’s water supply system. All water softeners use the same operating principle: They trade the minerals for something else, in most cases sodium. The process is called ion exchange. More…
Step by step instructions on installing replacement cartridges and sanitizing filter housings. It is highly recommended that you clean and sanitize your system once a year.
Step by step instructions on making a connection with Twist and Lock fittings. Twist-Lock fittings allow you to connect and disconnect tubing without the need of tools.
Step by step instructions on making a connection with SharkBite Push-To-Connect fittings. SharkBite fittings allow you to connect and disconnect pipes without the need of using PVC glue or welding copper.
A micron is a unit of measurement for how small of particles a filter will catch. The lower the micron size, the tinier the ‘holes’ in the filter cartridge are that allows water to pass through, ranging from 0.1 absolute to 150 microns.
Use our Pore Size Efficiency Guide to find out what micron size to use.
Pleated sediment cartridges remove dirt, rust and sediment from water while providing an increased surface area and longer life. Pleated filters down to 5 microns are washable and reusable.
Use our Pleated Sediment Cartridge Comparison to find the filter cartridge you need.
When brewing beer with tap or bottled water, chlorine and chloramine present in the water can combine with malt phenols in the wort to create a compound called chlorophenol, which can give the beer a medicinal taste.
View our Filtered Water for Home Beer Brewing guide.
Bottled water requires a lot of resources to manufacture and ship, and costs a lot more than reverse osmosis water.
Use our Bottled Water Cost Calculator to find out how much of an impact you have on the environment.