Water pollution and contaminated water supplies are a problem felt everywhere, not just in the developing nations. Even in industrialized countries, groundwater is often polluted with chemicals and minerals: a detriment to a person’s health and it gives drinking water an unpleasant taste. Many people are now choosing to install water purification systems into their homes to ensure that their water is clean and fresh tasting.
Some of the more popular water filtration systems include activated carbon filters, metallic alloy filters, and ceramic filters. These three kinds of filters work in essentially the same manner. They are porous materials that trap contaminant in their tiny crevices, allowing clean and filtered water to pass. While these filters are better than having no filter at all, they may not purify water completely. Particles can get through the system of pores and into the drinking water. In addition, once the filter becomes full of contaminants, it has to be changed.
In recent years, water filtration technology has advanced to the point where home reverse osmosis water purifiers have become available. Reverse osmosis systems have been used for industrial purposes for decades to decontaminate the water supplies for cities, process bottled water, and to desalinate seawater. Reverse osmosis purifying systems can clean water better than most kinds of water filtration systems available.
What is Reverse Osmosis?
In order to understand what reverse osmosis is and how it is helpful in the purification of water, it is important to know the principles behind osmosis. Osmosis is a chemical process in which fluid (i.e. water) moves from an area of high concentration to an area of low concentration through a semipermeable membrane. A semipermeable membrane is a thin surface that has microscopic holes in it that allows particles smaller than the hole to pass through to one side, while keeping particles that are larger than the holes on the other side. When an equal amount of fluid and particles of contaminants are on both sides of the semipermeable membrane, the whole system is balanced and in equilibrium, a state in which the transfer of particles across the semipermeable membrane stops.
Another term for the process of reverse osmosis is hyperfiltration. In reverse osmosis, the semipermeable membrane is used as a filter for contaminants. Here is how reverse osmosis works:
- Polluted water is held on one side of the semipermeable membrane.
- Pressure is exerted onto the polluted water, forcing it through the semipermeable membrane.
- The semipermeable membrane, being full of tiny holes, allows water molecules through, while preventing larger contaminants from passing.
- Purified water is collected on the other side of the semipermeable membrane.
In advanced reverse osmosis purification systems, a system called crossflow is used to keep the membrane from clogging. In a crossflow system, water is continuously passed through the membrane, allowing the contaminants to be swept away without clogging the membrane.
In home reverse osmosis purification systems, two kinds of semipermeable membranes are commonly used. The first is called Thin Film Composite (TFC). The second option in home reverse osmosis systems is a Cellulose Triacetate (CTA) membrane. In general, TFC membranes filter water better than CTA membranes because the holes in them are smaller and can capture more foreign particles. The one disadvantage to a TFC membrane is that it can be destroyed by exposure to chlorine in municipal tap water over a period of time. Most reserve osmosis purification systems have an activated carbon filter that removes chlorine to safeguard the membrane.
What Can Reverse Osmosis Filter?
Reverse osmosis is a very effective way of cleaning water, filtering out almost all contaminants that may be in home tap water. Here are some of the things that a reverse osmosis water purifying system can remove, listed by the effectiveness of the reduction:
- Removes: Arsenic, Most bacteria and viruses, Chlorine, Fluoride, Odors, Bad Tastes, Heavy metals, Nitrates, Debris, Sediment and Iron
- Reduces the amount of: Hydrogen sulfide, Benzene, Other volatile substances
- No effective removal: Radon
It should be noted that a reverse osmosis water purifier does not kill bacteria or viruses. In some cases, tiny viruses may pass through the semipermeable membrane and into the purified water if the membrane has been damaged due to prolonged exposure to chlorine. To safeguard against this, most reverse osmosis filtration systems are installed simultaneously with ultraviolet light filters that can kill pathogens.
Pros and Cons of Reverse Osmosis Water Purification
There are numerous pros and some cons to owning a reverse osmosis purification system. One advantage of a reverse osmosis system is that reverse osmosis is better than almost any water purification system for filtering out contaminants and pathogens. Reverse osmosis systems can also render water tasteless and odorless. Purified water also prevents rust and mineral build up in bathrooms, sinks, and pipes. Also, over the long term, reverse osmosis is inexpensive, costing less than 5 cents per gallon to filter. When compared with other filtration systems, it is a bargain.
The biggest drawback with a reverse osmosis purifier is that it requires a lot of water to maintain the pressure required to induce hyperfiltration. Of all the water that passes through a reverse osmosis system, only between 5 and 15% of the water that goes in becomes purified, leaving a tremendous amount of waste water. Home systems are also slow, producing between 15 and 20 gallons of purified water per day depending on the system. Finally, due to degradation of the semipermeable membrane over time by exposure to chlorine, bacteria and viruses can make their way into the purified water. As a result, many people choose to install UV filters along with their reverse osmosis purifiers.
Costs and Brands
For installation in a home, a reverse osmosis purification system can be quite costly. Initially, a homeowner will have to pay for the system and installation that can run between $300 and $5000 depending on the quality and capacity of the water purification system. Also, from time to time, the membrane will need to be replaced. Membranes cost between $100 and $300 dollars. In addition, carbon filters are needed to increase the longevity of the semipermeable membrane. These can cost between $50 and $100.
Finally, most homeowners choose to install an additional UV filtration system to kill bacteria and viruses. These can cost several hundreds of dollars in addition to installation fees. In recent years, another alternative to a house-wide reverse osmosis system is small portable units. These can cost as little as $150 and go up to $500. They can be placed in any room and can produce several gallons of purified water per day. Some popular brands include the GE Profile Reverse Osmosis Filtration System, the Aqua Pure Reverse Osmosis Drinking Water System, and The Tap Master Iron Reverse Osmosis Water Filtration System.
The End Result: Opt for RO
As pollutants in municipal water supplies increase, more people are looking into installing home water purification systems. While there are many kinds, none surpass reverse osmosis systems in terms of filtering out contaminants. For those interested in drinking the cleanest water available, reverse osmosis water purification systems should definitely be considered.