Reverse Osmosis~ 4 Stages Reverse Osmosis System

The different stages inside a residential Reverse Osmosis system

Domestic and commercial reverse osmosis water treatment system in general, is actually referring to a series of carefully selected water treatment methods used in combinations to achieve the best possible quality in supply water. The diagram on the left  shows the general schematic of a typical 4 stage RO water system.

Stage 1

The systems begins with normally a 1 to 5 micron sediment filters to screen out any large particulates including large iron slits, dust, turbidity. This will prevent any deposition of large particles onto the ultra fine RO membranes which typically in the order of 1 to 100 angstrom (1 angstrom = 1/10,000 micron or 1/10,000,000,000 meter of 1/10trillionth meter, this compare to human hair thickness with average diameter of approximately 750,000 angstrom or 75 micron).

Stage 2

The Carbon filter is then use to pick up about 90 to 95% of all the organic particles and remove the majority of chlorine in the water stream.  Under proper maintenance, the carbon filter will help to maintain the efficiency of RO system for longer service life.

Stage 3

Then the third step is the use of RO which is the heart of the system. The fine membrane as explain by previous article regarding the Reverse Osmosis.   It acts as surface filter with fine enough mesh to pass only a small amount of minerals and water molecules. Any long chain organic compound, including micro-organisms and also artificial compounds such as pesticide and weedicide will be screen out. Because of the ultra fine mesh size of the membrane, it will also block all harmful virus and other micro-organisms which may pass through in case of alternative filtration technology.

Storage Tank

Because of the high pressure drop of the Reverse Osmosis process in order to filter the water particles, the clean water stream has very slow flow rate and a temporary water reservoir tank is used to buffer the flow when no clean water is draw from the system. The clean water is collected in the tank when the system is in idle status and also the tank will act as a pressure buffer to smooth out any pressure changes between the two side of reverse osmosis membrane which will extend its life. A automatic shut off valve (whether it is a electronic or mechanical) is then used to shut off water supply to the RO system when the water tank is full.

Stage 4

There are sometimes small odors in the clean water which is a result of the interior finishing of the water tank and inner lining of the tubing. Thus a final post carbon filter is normally added as a final polish filter to remove such odors or taste and to give the great taste typical of spring water.

It is common for the sediment and the first carbon pre-filter to plug up and efficiency reduced by the end of service life cycle and the second carbon filter has thus little effect to the overall performance of the system. While adding a second activated carbon pre-filter to the system has no ill effect to the drinking water quality, the use of such system may be subject to the water source conditions including chlorine concentration, organic content (such as the case of having a no-pretreat surface water source), etc. and thus it is best to talk to your Perfect Life Water specialty agent for recommendation first.

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