Reverse osmosis (RO) is a technology that is used to eliminate a large number of water contaminants. Introduced in the 1970s through home purification systems in North America, this technology pushes water under pressure through a semi-permeable membrane known as reverse osmosis. This filters out contaminants and several compounds in the water. Large molecules and ions are left on one section of the membrane while smaller particles than water molecules remain in the drinking water. The best reverse osmosis systems ensure you that dangerous contaminants like nitrates, arsenic and lead are eliminated from your water.
Osmosis vs. Reverse Osmosis
Understanding osmosis will help you to fully understand the process and purpose of reverse osmosis.
Osmosis is one of the most important naturally occurring processes. It is a process where a more fragile saline solution has the tendency to move to a strong saline solution. Good examples of osmosis include the human kidneys absorbing water from our blood and the roots of a plant absorbing water from the soil.
Reverse Osmosis is the opposite of the Osmosis process. Unlike osmosis, reverse osmosis requires the application of energy to the more saline solution. It uses a semi-permeable membrane, known as RO membrane, which allows the water molecules to pass but blocks most of the organics, dissolved salts, pyrogens and bacteria. To push the water through the RO membrane, greater pressure must be applied (bigger than the pressure in osmosis). By applying great pressure, water is demineralized or deionized, eliminating a majority of contaminants, so you get pure, clean, and safe water.
How Does Reverse Osmosis Work?
A membrane-technology filtration process, reverse osmosis applies pressure to solutions when it is on one section of a selective membrane to eliminate several kinds of large ions and molecules from the solutions. This process leaves the solute on the membrane’s pressurized section, allowing the pure solvent to flow to the other section. So how does reverse osmosis work?
Pre-filter. Once the water enters the reverse osmosis, it passes through a pre-filter that shields the automatic switch off and the membrane from blocking with debris. The pre-filter stage filters out the large particles like the rust and deposits to extend the RO membrane’s life and to permit it to handle the smaller pollutants.
In some higher output reverse osmosis systems, the pre-filter contains activated carbon that eliminates both chlorine particles and other pollutants.
Membrane Filtration. The water then passes through the membrane, which is the operational center of the RO unit, where most of the miniscule particles trapped by the pre-filter are eliminated from the water channel and washed to the drain. Hydrogen and Oxygen molecules are allowed to pass through the microscopic pores of the membrane, which are the components of water. Most of the pollutants and liquefied solids are rinsed into the water stream’s drain and goes out the RO system.
The Final Filtration Stage. The reverse osmosis water is sent to the storage tank after the membrane filtering. The system will generate more water once the automatic shut-off sends a signal. The water passes through the final filtration stage (carbon filter when you switch on the faucet and draw water from the storage tank. At this stage, the remaining odors and tastes are eliminated from the water, giving you a better-tasting and nice-smelling clean, safe drinking water.
Type of Reverse Osmosis Systems
The types of reverse osmosis systems differ on the number of filters and membranes used.
- Under the Counter. These RO systems are installed together with the kitchen faucet, making it handy to get water. The number of filtration process depends on how it was designed by the manufacturer. It can be connected directly to the kitchen tap or any independent faucet, the drain or any cold water line. Most under the counter reverse osmosis systems can function up to 50-100 psi water pressure generating 50 gallons of clean, safe water in a day.
- Counter Top. This model is ideal for home and office use. The number of filtering stage depends on the brand or the manufacturer. There are some units that feature both hot and cold power switch. Counter top RO systems give you one and a half gallon of filtered, clean water in one hour. It is also portable, allowing you to bring it anywhere or transfer it from one place to another.
- Floor Type. These RO systems use at least 9 stages of water filtration process. Every stage eliminates certain types of pollutants. The 1st stage eliminates the organic pollutants that cause the foul smell and taste of water. The quality of water these systems produce is unquestionable because of the 9 stages of filtration. However, the process of filtration is relatively slow, giving you a little over one gallon of water in one hour.
The Filtration Stages of RO Systems
The number of filtration stages of a reverse osmosis system depends on the manufacturer, with some featuring 5, 6, 7, or even 9 stages of filtration. However, the basic filtration stages of RO systems are as follows:
- 1st stage or sedimentation allows the water to passthrough a sediment filter to remove dust, silt, and other large particles.
- 2nd stage is also known as granulated activated carbon stage that removes chlorine, mineral oil and the bad taste of the water.
- 3rd stage uses a denser carbon filter to eliminate the remaining chlorine and odor in the water.
- 4th stage is the reverse osmosis stage, pushing the water into a very fine filter to eliminate 99% of the remaining water pollutants like fluoride.
- 5th stage utilizes a polishing carbon filter where the stored water in the tank is kept fresh.
- 6th stage is the alkalinization process, where the pH of water is kept at 7 or more using good minerals like calcium and magnesium.
- 7th stage is the UV process to kill any viruses or bacteria in the water.
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The Common Basic Components Found in All Reverse Osmosis Systems
- Cold Water Supply Line Valve. This line valve is the reverse osmosis system’s source of water. It consists of a tube that fastens to the inlet side of the pre-filter of the RO system.
- Pre-filter(s). From the cold water line valve, the water goes into the RO pre-filter initially. Depending on the brand, the pre-filter can be more than one, but the most common are the sediment filters. The pre-filter eliminates dirt, sand silt, and other sediments in the water. Carbon filters may additionally be used to eliminate chlorine but can affect the thin film composite (TFC) and the thin film material (TFM) membranes. RO systems that contain cellulose tri-acetate (CTA) membranes do not use carbon pre-filters.
- RO Membrane. This is the core of most reverse osmosis systems. Most RO systems use the spiral wound, which offers two choices: 1) CTA, which tolerates chlorine, and 2) TFC/TFM, which is non-chlorine tolerant.
- Post Filter(s).The pre-filtered water goes through the post filter stage after leaving the storage tank and before it goes out through the reverse osmosis tap. The post filters normally consist of the granular activated carbon or the carbon block form, where remaining odors and tastes are removed from the water.
- Automatic Switch off Valve. RO systems are fitted with an automatic switch off valve, so water stops from entering the membrane once the storage tank is full. This prevents the water from flowing or leaking from the drain. The switch off valve opens automatically once the pressure in the tank drops, so water starts to flow through the membrane with the waste water flowing down the drain.
- The Check Valve. Situated in the outlet end housing of the reverse osmosis membrane, this valve stops the rearward flow from the storage tank. A rearward flow could damage the membrane of the RO system.
- Flow Control.The flow control, situated in the drain line tubing, regulates the flow of water through the membrane. It maintains the required flow rate to attain the best quality drinking water that is dependent on the gallon capacity of the membrane. It also helps keep the pressure on the membrane’s inlet side. The absence of a flow control would make the incoming water from the tap to take the least resistance path so it would flow down the drain, generating a small amount of drinking water.
- The Storage Tank. The standard reverse osmosis system storage tank has a 2.5 gallons capacity. Water is pressurized inside the tank by a bladder when it is already full.
- RO Faucet. All RO units have their own tap, which is normally installed on the kitchen sink. An air-gap tap is used for areas that require plumbing codes.
- The Drain Line.Running from the outlet end of the RO membrane housing to the drain, it is utilized to get rid of contaminants and impurities in the tap water. The flow control is installed in the drain line, too.
The Popularity of Reverse Osmosis Water
Reverse osmosis water has become very popular since it was launched in the 70s as a home water purification system. This is because it removes several water pollutants, such as arsenic, copper, selenium, fluoride, and other organic chemicals. Most bottled water companies use RO water.
Advantages of Reverse Osmosis Systems
- Reverse osmosis systems removeunhealthy contaminants, including the smallest particles. Although boiling water and ultraviolet light destroy bacteria, they do not eliminate small particles of inorganic contaminants like chemicals and metals.
- They eliminate dissolved minerals and other pollutants that cause the unpleasant smell and opaque look of water.
- RO systems have long-lasting membrane filters. Filters in other water filtration systems last only for two to four weeks, requiring you to replace it often.
- They are compact.Reverse osmosis systems require little space compared to other water purification systems.
- Reverse osmosis systems are perfect for people with heart disease. They remove 99% of bacteria and majority of the salt and pyrogenic substances in the water that can cause harm to people with heart disease.
- They remove all the heavy metals that endanger human health, such as mercury, lead and selenium, including animal waste and chemicals.
- RO systems are designed to start and shut off automatically saving you from checking the unit every now and then.
- They are low-cost. RO system gives you clean, safe and delicious water that cost a few pennies per gallon compared to buying bottled water.
- Reverse osmosis systems are environment-friendly. They do not produce any chemicals and require a small amount of power.
Disadvantages of Reverse Osmosis Systems
- The reverse osmosis process is slow. To push tap water through the semi-permeable membrane, RO uses household water pressure and this takes time, making the process slow. You need to wait for the process to refill the tank if you need lots of filtered water immediately and to empty the holding tank of the system.
- They remove a high percentage of fluorideadded to several municipal water systems in the U.S. Adding fluoride to water systems in all municipalities is the state government’s move to stop cavities in children. However, it must be noted that too much fluoride can lead to several side effects.
- Reverse osmosis systems eliminate a huge majority of salts and minerals in the water. The RO membrane traps magnesium, calcium and potassium, essential minerals for bone health and in the transmission of electrical signals from the human brain. These minerals are essential in maintaining the taste of the water and the fluid balance in the body. The absence of these minerals in drinking water reduces pH levels, making the water acidic. High levels of acidity promote degenerative diseases like arthritis and osteoporosis.
- They waste a large portion of water. Lots of water are wasted particularly by the household RO system because of low back pressure. These systems waste two to three gallons of water per one gallon of purified water that is produced. The extensive systems (municipal/industrial) are more efficient because these produce higher pressure required for a more efficient reverse osmosis filtration process.
The Benefits of Reverse Osmosis Systems
- Improves the odor, taste, and appearance of water. Nitrates, lead, iron, sulfur-based compounds, and other chemical residues give water a bad taste. RO systems remove these substances, providing safer, cleaner and better-tasting water.
- Highly efficient water purification process. Reverse osmosis systems eliminate most of the contaminants, such as lead. Higher levels of lead in the body reduced fertility, cause high blood pressure, and nerve damage. Brain damage and anemia in children can occur from lead toxicity. Parasites like cryptosporidium that causes fever, stomach cramps, and diarrhea are filtered out.
- Flushes out contaminants. RO systems are great in eliminating contaminants such as arsenic, copper, selenium, fluoride, and several other organic chemicals giving great-tasting water.
- Energy-efficient. Reverse osmosis purification systems turn off automatically once the tank is full of filtered water. This saves you on energy costs and no water is wasted.
- Guaranteed quality water. RO systems provide you guaranteed quality water at a lower cost per gallon.
- Very convenient. These water purification systems are very convenient because they can fit under the sink, placed on the counter or placed on the floor. There is even an RO system that offers a continuous flow of filtered water.
- Easy to maintain. RO systems are easy to clean. Some brands require changing the filters every 3-6 months
Factors to Consider when Choosing a Home Reverse Osmosis System
We have discussed the advantages, disadvantages and benefits of reverse osmosis systems, as well as their basic process that differs on the number of filtration stages. So now, we will discuss the factors toconsider when buying a home RO system for your home or office.
The Filtration Stages
The more popular brands of RO systems feature five to seven filtration stages. Those with six to seven include an alkaline/pH filter stage that can replace lost minerals, such as calcium and magnesium. The 5-filtration stage RO systems are fairly the same in their goal of removing dust, rust, and sediments on the first stage; eliminating unpleasant odors, tastes, colors and cloudiness on the second and third stage by using carbon filters; eliminating chemicals like arsenic, chlorine, radium, lead, and fluoride in the fourth stage; and refining the taste of water on the fifth stage.
A reverse osmosis system that features more filtration stages would naturally be expensive and more long-term running costs because you need to change more filters. However, it produces better-tasting water.
Production Rate of the Water
This refers to the amount of water generated by the RO system per day, which is usually measured in GPD (gallons per day). The best reverse osmosis systems generate between 50 to over 90 GPD. Manufacturers, though, do not say that these amounts are seldom attained. The amount generated by RO systems depends on several things, such as –
- incoming water pressure
- water temperature (higher water temperature is better)
- the quality of the original water supply
An 80% water production rate of the value stated by the manufacturer is perhaps based on the average water pressures and supplies in an average household. A small reverse osmosis system that generates 80% of the target gallon/day can deliver 40 gallons (151L) of clean, safe water per day. This gives an estimated 1.66 gallons (6.5L) in an hour, assuring you of having an adequate amount of clean and safe water from your tap.
Effectiveness, Duration, and Cost of the Filters
Replacing the filters is the long-standing main and running cost of RO systems, which depends on the price of the filters. It is without a doubt that the cheap ones are not durable and will cost you more in the end. Most filters last from 6 to12 months. The effectiveness of the filters is another aspect to consider. The most effective filters are definitely expensive. High-quality filters may be a little pricey, but they are long-lasting and works efficiently. Remember that quality is more important than the cost.
Reverse Osmosis Systems Maintenance Tips
Correct maintenance is necessary regardless of the appliance, device or unit and this also applies even to the best reverse osmosis systems. Following are the basic RO system maintenance tips that every user should observe.
- Change the pre-filter per manufacturer’s recommendation.The pre-filters are the primary collectors of sand, dirt, deposits and other sediments prior to pushing the water to the semi-permeable membrane. The impurities can clog the pre-filter if not properly maintained that can lead to damaged membranes.
- Replace the carbon filters as recommended by the manufacturer. The chlorine filtered out by the carbon filters can rupture the semi-permeable membrane so it has to be replaced as indicated in the product’s brochure. Failure to replace the carbon filters leads to slow production of water until no water is generated. This occurrence indicates that the reverse osmosis system,as well as the filters and membrane, were completely utilized. Always purchase the filters recommended by the manufacturer to ensure its compatibility and dependability with the RO system for excellent performance.
- Yearly RO system recharge and sanitization. Schedule a yearly RO system check and maintenance by a professional water treatment service provider. The manufacturer may suggest a specific water treatment service provider so read and review the manual. A properly serviced and maintained RO system (including replacement of wear out parts like faucet and tank) will last up to 10 – 15 years.
- Read the manual of your RO system prior to installation and follow the filter and membrane replacement and the yearly cleaning and sterilizing schedules.
Tips for Using Revese Osmosis System
Test your water. A comprehensive chemical analysis of your water is necessary to know the level of pollutants present in the water and to know how to deal with them. Request for a copy of the water test results report from your water handling company so you can choose the best RO system suitable to your situation. The reverse osmosis water system is recommended in areas where there are high dissolved elements in the water system.
RO System Installation. Installing an RO unit is easy and most products come with an installation guide. Most of them are mounted under the sink. It would only take you about 30 minutes to install an RO system, especially if you follow the installation guide correctly. Just remember not to place the storage tank in an upright position and ensure that the area where you place the tank is warm during winter.
Ensure that the water pressure is at a moderate level. Take extra care of the RO membrane because it is the most expensive part. Refrain from any activity that may damage it, such as a very high water pressure. Always follow the manufacturer’s instructions on keeping the pressure of water at a moderate level.
Change the RO filters. The filters will ultimate require replacement after quite some time. Make sure to purchase only excellent quality filters or those that are recommended by the manufacturer. This will prevent you from incurring more expenses.
Schedule a routine maintenance for the RO membrane.Some particles may seep in the porese of the membrane that can lead for the membrane to break or crack. Keep your reverse osmosis system working optimally all the time by conducting a regular maintenance scheme. view more click here
Reverse osmosis systems are by far one of the most used water treatment processes in the US, as well as in more than a hundred countries all over the world.The RO systems industry has reached $8 bn globally, as wealthier countries in the West and in the oil-rich areas spend more money and capital in building and operating RO water purification facilities. The shortage for potable and safe drinking and potable water is said to be a severe concern globally in 15 years. With reverse osmosis systems, people all over the world are assured of having clean and safe drinking water from their faucet.
With this news, it is about time to think about your and your family’s health. Investon a quality reverse osmosis system now! Your investment is worth it, particularly with the best reverse osmosis systems–protecting you and your family from dangerous toxins present in ground and tap water.