Reverse Osmosis
The reverse osmosis process draws water through an extremely fine membrane, which acts like an extremely fine filter to create drinkable water. The contaminated water is on one side of the membrane and the osmotic process starts as pressure is applied. It takes a lot of pressure and processes water slowly, but it creates finely filtered water.
The reverse osmosis drinking water filter provides the most effective purification of drinking water for the home. Although the technology itself has been around for three to four decades, home drinking water purifiers using RO remain uncommon. Despite its many advantages, there are valid reasons for it lack of popularity.
Advantages
The first and biggest advantage of reverse osmosis filters is that they remove all impurities and contaminants from your drinking water. RO was invented in the 70's as a cheaper way than distillation to remove salt from sea water. Today, RO is widely used for desalination, kidney dialysis and waste reclamation. RO home filtration systems are as effective as their industrial counterparts.
Unlike filtration systems made from carbon, RO filters can remove all heavy metals (including lead, mercury and copper) as well as the nitrites and nitrates in fertilizers. Like carbon filters, reverse osmosis purifiers also remove sediment, chlorine and organic poisons (herbicides and pesticides used in agriculture). This wide-ranging effectiveness should logically make them the first choice for any family.
Pros: Removes a wide range of contaminants, including dissolved solids and arsenic.
Cons: Requires plumbing to be re-routed. Must be periodically cleaned and sanitized with bleach. Is slow and creates about 4 gallons of waste water for every gallon filtered. Removes all minerals, and some health experts believe that prolonged drinking of water without minerals can damage one’s health.
Typical unit, costs several thousand dollars, a very high price when compared to high-end carbon purification systems which normally cost in the hundreds of dollars.
Third major reason is the cost of replacement filter cartridges. While reverse osmosis filter cartridges will last as long as carbon filter cartridges (normally six months), the cost of each RO cartridge is much higher.
Reverse osmosis is, unfortunately, very inefficient compared to filtration using activated carbon. While industrial RO systems provide nearly 50% efficiency, home RO filters only provide 5% to 15% efficiency. The remaining 85% to 95% of the water is discarded. This is very wasteful compared to GAC and powdered carbon block filters which only slow down the flow but do not actually waste any water.
While all methods of water filtration require a reasonable level of pressure, reverse osmosis home purification systems require the highest pressure ( 55p.s.i. - 80 p.s.i.) to work properly. Homes with low pressure would need to install additional equipment to use RO filters. This would naturally add greatly to both the purchase and maintenance cost.
Conclusion
A reverse osmosis drinking water filter provides the best protection of your drinking water. Unfortunately, its high cost (mainly purchase, installation, maintenance and operation) makes it not viable for many people. Alternatives include high-end carbon filters with ion exchange.
Alternatives
Given the disadvantages of reverse osmosis filtration, it is fortunate that there are alternatives for those of you who still need to remove heavy metals and nitrites/nitrates from your tap water. Carbon filters work well for removing sediment, chlorine and organic chemicals. So they still form the base of our water purification. After the tap water passes through the activated carbon, it would need to go through a resin ion exchange unit to remove the remaining contaminants (heavy metals and fertilizer).
Many high end filters provide both the carbon cartridge and ion exchange cartridge to provide complete purification of drinking water. While they are cheaper than a reverse osmosis filter, they are more expensive than normal carbon filters.
REVERSE OSMOSIS UNDER THE SINK
$150 at Costco
