How Reverse Osmosis Works
What is Reverse Osmosis?
Reverse osmosis, also known as hyper-filtration, is the finest water filtration available today. It is the most common treatment technology used by premium bottled water companies. It is effective in eliminating or substantially reducing a very wide array of contaminants, and of all technologies used to treat drinking water in residential applications, it has the greatest range of contaminant removal. Reverse osmosis will allow the removal of particles as small as individual ions. The pores in a reverse osmosis membrane are only approximately 0.0005 micron in size (bacteria are 0.2 to 1 micron & viruses are 0.02 to 0.4 microns).
Reverse osmosis (RO) units remove substantial amounts of most inorganic chemicals (such as salts, metals, minerals) most microorganisms including cryptosporidium and giardia, and most (but not all) inorganic contaminants.
Reverse osmosis successfully treats water with dissolved minerals and metals such as aluminum, arsenic, barium, cadmium, chloride, chromium, copper, fluoride, magnesium, iron, lead, manganese, mercury, nitrate, selenium, silver, sulfate, and zinc. RO is also effective with asbestos, many taste, color and odor-producing chemicals, particulates, total dissolved solids, turbidity, and radium. When using appropriate activated carbon pre-filtering (commonly included with most RO systems), additional treatment can also be provided for such "volatile organic contaminants” (VOCs) as benzene, MTBE, trichloroethylene, trihalomethanes, and radon.
Essentially, reverse osmosis is capable of rejecting bacteria, salts, sugars, proteins, particles, dyes, heavy metals, chlorine and related by-products, and other contaminants that have a molecular weight of greater than 150-250 daltons. The separation of ions with reverse osmosis is aided by charged particles. This means that dissolved ions that carry a charge, such as salts, are more likely to be rejected by the membrane than those that are not charged, such as organics. The larger the charge and the larger the particle, the more likely it will be rejected.
Applications For Reverse Osmosis
Reverse osmosis is an excellent choice for almost all home water purification needs. It is the most recommended solution for individuals on a pre-treated municipal water system. While reverse osmosis can be very effective in removing bacteria and viruses, it is not recommended that reverse osmosis be the only level of purification for water that contains or may contain biological contaminants (untreated well or lake water, for instance). For these applications consider a combined reverse osmosis / ultraviolet system or the addition of a complementary whole-house ultraviolet system for maximum effectiveness and protection against bacteria and viruses. Since membranes are subject to degrading by chlorine, iron, manganese, and hydrogen sulfide, and to bacterial attack, a sediment pre-filter and an activated carbon pre-filter and/or post-filter should be included with your reverse osmosis system. Water softeners can be used in advance of the RO system when household water is excessively hard to prevent pre-filter and membrane fouling. RO systems are generally the best choice for water contaminated with high nitrite levels as might be found in agricultural areas.
How Reverse Osmosis Works
Water pressure is used to force water molecules through a very fine membrane leaving the contaminants behind. Purified water is collected from the "clean" or “permeate” side of the membrane, and water containing the concentrated contaminants is flushed down the drain from the "contaminated" or “concentrate” side. The average RO system is a unit consisting of a sediment/chlorine pre filter, the reverse-osmosis membrane, a storage tank, and an activated-carbon post filter.
A semi-permeable membrane, like the membrane of a cell wall or a bladder, is selective about what it allows to pass through, and what it prevents from passing. These membranes in general pass water very easily because of its small molecular size; but also prevent many other contaminants from passing by trapping them. Water will typically be present on both sides of the membrane, with each side having a different concentration of dissolved minerals. Since the water is the less concentrated solution seeks to dilute the more concentrated solution, water will pass through the membrane from the lower concentration side to the greater concentration side. Eventually, osmotic pressure will counter the diffusion process and an equilibrium will form.
RO forces water with a greater concentration of contaminants (the source water) into a tank that contains water with an extremely low concentration of contaminants (the processed water). High water pressure on the source side is used to "reverse" the natural osmotic process, with the semi-permeable membrane still permitting the passage of water while rejecting most of the other contaminants. The specific process through which this occurs is called ion exclusion, in which a concentration of ions at the membrane surface from a barrier that allows other water molecules to pass through while excluding other substances.
Semi-permeable membranes have come a long way from the natural pig bladders used in the earlier osmosis experiments. Before the 1960's, these membranes were too inefficient, expensive, and unreliable for practical applications outside the laboratory. Modern advances in synthetic materials have generally solved these problems, allowing membranes to become highly efficient at rejecting contaminants, and making them tough enough to withstand the greater pressures necessary for efficient operation.
Even with these advances, the "reject" water on the source side of a Reverse Osmosis (RO) system must be periodically flushed in order to keep it from becoming so concentrated that it forms a scale on the membrane itself. RO system also typically require carbon pre-filter for the reduction of chlorine, which can damage an RO membrane; and a sediment pre-filter is always required to ensure that fine suspended materials in the source water do not permanently clog the membrane. Hardness reduction, either through the use of water softening for residential units or chemical softening for industrial use, may also be desirable in hard water areas.
Though slower than a water filter, residential RO systems can typically purify more than 35 gallons of water per day…far more than the typical requirements for drinking and cooking in the home. Also, they do not use electricity, but RO systems do waste water. About 4 gallons of concentrate wastewater are flushed down the drain for each gallon of filtered water produced.
Two common types of household RO membranes are the Thin Film Composite (TFC or TFM) membrane and the Cellulose Triacetate (CTA) membrane. The main differences between the two types are filtration ability and chlorine tolerance. The CTA membrane is chlorine tolerant, but is more susceptible to fouling from bacteria, and it only rejects 93% of standard contaminants. The TFC/TFM membranes reject 98% of standard contaminants on average, are less susceptible to organic fouling, but it can only treat chlorine free water. Carbon pre-treatment must be used with a TFC/TFM membrane when purifying chlorinated municipal water supplies.
Typical Point of Use Reverse Osmosis System
Countertop units typically have an un-pressurized storage tank. Under-sink units typically have a pressurized accumulator storage tank where the water pressure tends to increase as the tank fills. This pressurized system provides sufficient pressure to move the water from the under-sink storage tank to the faucet.
For residential use, a modern 4-stage RO system that is built with NSF listed components and WQA certified under NSF / ANSI 58 standards will provide many years of extremely high-quality purified water. These systems generally consist of the following parts:
Reverse osmosis, also known as hyper-filtration, is the finest water filtration available today. It is the most common treatment technology used by premium bottled water companies. It is effective in eliminating or substantially reducing a very wide array of contaminants, and of all technologies used to treat drinking water in residential applications, it has the greatest range of contaminant removal. Reverse osmosis will allow the removal of particles as small as individual ions. The pores in a reverse osmosis membrane are only approximately 0.0005 micron in size (bacteria are 0.2 to 1 micron & viruses are 0.02 to 0.4 microns).
Reverse osmosis (RO) units remove substantial amounts of most inorganic chemicals (such as salts, metals, minerals) most microorganisms including cryptosporidium and giardia, and most (but not all) inorganic contaminants.
Reverse osmosis successfully treats water with dissolved minerals and metals such as aluminum, arsenic, barium, cadmium, chloride, chromium, copper, fluoride, magnesium, iron, lead, manganese, mercury, nitrate, selenium, silver, sulfate, and zinc. RO is also effective with asbestos, many taste, color and odor-producing chemicals, particulates, total dissolved solids, turbidity, and radium. When using appropriate activated carbon pre-filtering (commonly included with most RO systems), additional treatment can also be provided for such "volatile organic contaminants” (VOCs) as benzene, MTBE, trichloroethylene, trihalomethanes, and radon.
Essentially, reverse osmosis is capable of rejecting bacteria, salts, sugars, proteins, particles, dyes, heavy metals, chlorine and related by-products, and other contaminants that have a molecular weight of greater than 150-250 daltons. The separation of ions with reverse osmosis is aided by charged particles. This means that dissolved ions that carry a charge, such as salts, are more likely to be rejected by the membrane than those that are not charged, such as organics. The larger the charge and the larger the particle, the more likely it will be rejected.
Applications For Reverse Osmosis
Reverse osmosis is an excellent choice for almost all home water purification needs. It is the most recommended solution for individuals on a pre-treated municipal water system. While reverse osmosis can be very effective in removing bacteria and viruses, it is not recommended that reverse osmosis be the only level of purification for water that contains or may contain biological contaminants (untreated well or lake water, for instance). For these applications consider a combined reverse osmosis / ultraviolet system or the addition of a complementary whole-house ultraviolet system for maximum effectiveness and protection against bacteria and viruses. Since membranes are subject to degrading by chlorine, iron, manganese, and hydrogen sulfide, and to bacterial attack, a sediment pre-filter and an activated carbon pre-filter and/or post-filter should be included with your reverse osmosis system. Water softeners can be used in advance of the RO system when household water is excessively hard to prevent pre-filter and membrane fouling. RO systems are generally the best choice for water contaminated with high nitrite levels as might be found in agricultural areas.
How Reverse Osmosis Works
Water pressure is used to force water molecules through a very fine membrane leaving the contaminants behind. Purified water is collected from the "clean" or “permeate” side of the membrane, and water containing the concentrated contaminants is flushed down the drain from the "contaminated" or “concentrate” side. The average RO system is a unit consisting of a sediment/chlorine pre filter, the reverse-osmosis membrane, a storage tank, and an activated-carbon post filter.
A semi-permeable membrane, like the membrane of a cell wall or a bladder, is selective about what it allows to pass through, and what it prevents from passing. These membranes in general pass water very easily because of its small molecular size; but also prevent many other contaminants from passing by trapping them. Water will typically be present on both sides of the membrane, with each side having a different concentration of dissolved minerals. Since the water is the less concentrated solution seeks to dilute the more concentrated solution, water will pass through the membrane from the lower concentration side to the greater concentration side. Eventually, osmotic pressure will counter the diffusion process and an equilibrium will form.
RO forces water with a greater concentration of contaminants (the source water) into a tank that contains water with an extremely low concentration of contaminants (the processed water). High water pressure on the source side is used to "reverse" the natural osmotic process, with the semi-permeable membrane still permitting the passage of water while rejecting most of the other contaminants. The specific process through which this occurs is called ion exclusion, in which a concentration of ions at the membrane surface from a barrier that allows other water molecules to pass through while excluding other substances.
Semi-permeable membranes have come a long way from the natural pig bladders used in the earlier osmosis experiments. Before the 1960's, these membranes were too inefficient, expensive, and unreliable for practical applications outside the laboratory. Modern advances in synthetic materials have generally solved these problems, allowing membranes to become highly efficient at rejecting contaminants, and making them tough enough to withstand the greater pressures necessary for efficient operation.
Even with these advances, the "reject" water on the source side of a Reverse Osmosis (RO) system must be periodically flushed in order to keep it from becoming so concentrated that it forms a scale on the membrane itself. RO system also typically require carbon pre-filter for the reduction of chlorine, which can damage an RO membrane; and a sediment pre-filter is always required to ensure that fine suspended materials in the source water do not permanently clog the membrane. Hardness reduction, either through the use of water softening for residential units or chemical softening for industrial use, may also be desirable in hard water areas.
Though slower than a water filter, residential RO systems can typically purify more than 35 gallons of water per day…far more than the typical requirements for drinking and cooking in the home. Also, they do not use electricity, but RO systems do waste water. About 4 gallons of concentrate wastewater are flushed down the drain for each gallon of filtered water produced.
Two common types of household RO membranes are the Thin Film Composite (TFC or TFM) membrane and the Cellulose Triacetate (CTA) membrane. The main differences between the two types are filtration ability and chlorine tolerance. The CTA membrane is chlorine tolerant, but is more susceptible to fouling from bacteria, and it only rejects 93% of standard contaminants. The TFC/TFM membranes reject 98% of standard contaminants on average, are less susceptible to organic fouling, but it can only treat chlorine free water. Carbon pre-treatment must be used with a TFC/TFM membrane when purifying chlorinated municipal water supplies.
Typical Point of Use Reverse Osmosis System
Countertop units typically have an un-pressurized storage tank. Under-sink units typically have a pressurized accumulator storage tank where the water pressure tends to increase as the tank fills. This pressurized system provides sufficient pressure to move the water from the under-sink storage tank to the faucet.
For residential use, a modern 4-stage RO system that is built with NSF listed components and WQA certified under NSF / ANSI 58 standards will provide many years of extremely high-quality purified water. These systems generally consist of the following parts:
• Stage 1 Pre-Filter – 5-micron Sediment Pre-Filter to capture trace sediment and invisible water-borne physical particles, preventing pre-mature clogging of the stage 2 carbon filter. (Replace every year)
• Stage 2 Pre-Filter - 10-micron activated carbon block to absorb VOC (volatile organic chemicals) such as herbicides, pesticides, chlorine, and chlorine byproducts (i.e THM, chloramines). The carbon block prepares water to enter the reverse osmosis element. (Replace every year).
• Stage 3 Membrane - High rejection (up to 98%) TFC (Thin-Film Composite) membrane to reject a wide range of Total Dissolved Solids (TDS). The product water is stored in the storage tank, while the reject water is automatically flushed down the drain. (Replace every 2-3 years).
• Stage 4 Post Filtration Polisher - In-line GAC (granular activated carbon) filter to remove volatile gases, bad taste and odor from product water. This is the final 'polishing' stage before consumption. (Replace every year).
• Shut-Off Valve - The shut-off valve closes the feed water to the membrane when the pressure in the Tank has reached "full". Based on the system design, this valve can be hydraulically or electrically activated.
• Storage Tank - Storage tanks for residential applications come in 3 and 5 gallon size, larger ones for commercial applications. Tanks must be pressurized to facilitate water flow from the tank to the faucet via a GAC polishing filter.
Join our mailing list for the latest offers & information!
Each of our systems is carefully selected to deliver the highest quality performance and provide many years of the purest and best-tasting water for you and your family. Since water is the essence of all life, healthy living begins with consuming adequate amounts of water for proper hydration…and water that is essentially free of potentially harmful contaminants. Just select the category above that suits your preferences, and we will promise you not only outstanding products at the lowest possible price…but also a shopping experience that makes you feel good and guarantees your satisfaction!