Comparisons of Ultra Filtration and Reverse Osmosis

Drinking CowayWhat is Reverse Osmosis? Reverse osmosis, also known as hyper filtration, is a membrane filtration technology in which water is forced by pressure through a semi-permeable membrane allowing the water to pass through while rejecting the larger contaminants (think of a strainer catching peas but allowing the water to pass through). In this regard, reverse osmosis is similar to micro filtration and ultra filtration.  However, reverse osmosis differs from these two technologies in that with micro filtration and ultra filtration the water is forced straight through a semi-permeable membrane which traps the larger contaminants. 

Reverse osmosis systems are T shaped forcing some of the water straight through the top of the ‘T’ and through the membrane while the rest of the water is swept down the base of the ‘T’ to clean the contaminants off of the membrane.  This process keeps the membrane clean and free of contaminants. 

Because of this, reverse osmosis systems have a holding tank for the purified water while the excess water goes down the drain in the system.  As a result, typical reverse osmosis systems waste four gallons of water for every one gallon of purified water.

Ultra filtration is membrane technology without all the wasted water. The main differences between the two methods is that reverse osmosis membrane pores are usually a little smaller, ultra filtration does not require as much pressure as RO and the water is purified as it is used with ultra filtration rather than being purified hours or days before it is used with RO systems.

Reverse osmosis systems must use storage tanks to hold the water before use. For counter top RO systems and most larger permanently installed units, the storage tanks are maintained at atmospheric pressure. Where as water is added to the tank, the air charge is compressed and the pressure in the tank rises. The elevated pressure then moves the drinking water from the storage tank to the faucet.  This storage tank system can cause a drop in the water production rate due to the fact that the accumulated pressure in the storage tank acts as backpressure on the membrane so when the tank pressure increases, the differential pressure across the membrane decreases.

Another draw back of Reverse Osmosis can be servicing the system. Like all water treatment units, the quality of water produced by a reverse osmosis system will be directly affected by the frequency of the systems service. If a reverse osmosis system is left unattended, their can be total failure of the system which will result in contamination of the water. Most reverse osmosis systems on the market today do not come with any type of monitoring devices to tell you when your system needs to be serviced.

Penapis Coway not only offers complete purification by filtering up to 0.0001 micron, they also come with free changing filter services by Coway Lady. They also have monthly affordable plan as well, owning a high quality water filter is now cheaper and owning them is a must for one’s health. If you’re thinking to get one, you may contact Coway representative here. Also see their RO water filter range.


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