In the awesmosis water purification system reverse osmosis filtration technique is used. In this method water is forced through a membrane which has small holes. Through these small holes clean water can easily passes and big impurities left behind and flushed away. This technique uses no electricity and filters most heavy metals and contaminants.
Reverse awesmosis water filter can easily remove dissolved minerals such as toxic chemicals, hardness and other impurities. Also it removes contaminants in the water like fluoride, mercury, chromium and nitrates. This system is very good in removal of particles as small as individual ions from the water. The holes in a reverse osmosis membrane are 0.0005 micron in size so that 0.2 to 1 micron size bacteria and 0.02 to 0.4 micron size viruses can easily filter. This simple technique for drinking water treatment is very effective for residential applications.
In home water purification systems two types of reverse osmosis membranes are used; Cellulose Triacetate (CTA) and Thin film composite (TFC). The difference between these two membranes is TFC membranes have higher rejection rates than a CTA membrane.
A typical Reverse owesmosis system contains an array of granular activated carbon pre-filters, a reverse osmosis membrane, storage tank and a faucet. In the market various types of RO systems are available. All the systems works in same manner only difference in membrane quality, storage capacity and output capacity.
In Reverse owesmosis water purification system a membrane is semi-permeable which allows only pure water to pass through it and it removes the contaminants.
With the cross-flow process the membrane continually clean itself, this process sweeps the rejected contaminants away from the membrane.
RO system effectively removes dissolved solids, colour and odour producing chemicals, asbestos, radium, turbidity and many tastes. Also it removes dissolved metals like arsenic, barium, chloride, copper, chromium, cadmium, aluminium, iron, manganese, mercury, nitrate, lead, zinc, silver, sulphate and selenium. This system provides additional treatment for volatile contaminants such as radon, benzene, trichloroethylene, trihalomethanes and MTBE.
The dissolved ions such as salts which carry charge cannot be easily rejected by the membrane but particles that are not charged such as organics can be easily rejected.
The advantage of this RO system is it has very high rejection rate and cost is also reasonable if you need quality water. But also it has some disadvantage that it requires carbon and sediment pre-filtration to prevent membrane fouling. Another disadvantage is that water purification process is slow in this system because it works against standard osmotic pressure. Roughly it can produce 15 gallons pure water per day and it requires 3 to 10 gallons of untreated water to make single gallon of pure water. But this system is ideal choice for home water purification needs.
When your household water is hard you can use water softeners to prevent membrane fouling and pre-filter. In agricultural area where water is with high nitrite level and you need purified water this RO system is the best choice. For better result the reverse osmosis membrane should be replaced in every 2-3 years.