
There are systematic equipment designed in order to abtain lower concentration
water (clear potable water) by using the method of reverse osmosis from
higher concentration water (polluted mains water) It is possible to reverse
the osmosis phenomenon which is a natural incident, by applying pressure.
When pressurized water is passed through the membrane wrapped artificial
rollers, most of the solid particles are held and disposed together with waste
water. Water with much lower concentration passing through thin membrane
pores is used as potable water. Before water enters into the membrane, in
order for the rough residues and chloride which is used in water disinfection
to be held, a pre-filtration proces such as sediment filter, carbon filter is usded.
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When semi-permeable membrane is placed in between two water column of
same volume but different concentrations in a U-tube, while water molecules
pass through the pores, several solid material particles having bigger size in
dissolved state can not pass through those pores. Passing rate is related to
concentration ratio, temprature and pressure. This passing continues until the
concentration ratio at both sides are equal. The pressure originating from the
potential energy of this increasing water column is balanced by the Osmotic
Pressure. Thet is to say, internal enetgy on the side with lower concentration is
balanced by the potential ebetgy of the excess in the water column on the side
with higher concentration.
On the condition the if a pressure equal to the pressure to be formed by the
excess in the water column is applied to the side with higher concentration, this
phenomenon called Osmosis does not take place. Furthermore, if a pressure
higher than this level is applied, Osmosis phenomenon is reversed. In spite of the
fact that amount is less, water molecules in the side with higher concentration
start to pass to the side with lower concentration. This phenomenon realized by
force of pressure is called Reverse Osmosis.
Reverse Osmosis is used to separate the solid matters dissolved in water. The
purpose in water purification is to convey the water molecules in water with high
concentration (polluted water) to the water side with lower concentration. Osmosis
take place conversely. In Reverse Osmosis, osmotic pressure surmounted by
application of pressure and the phenomenon is reversed and the purpose is achieved.
Figure 1. Osmosis and Reverse Osmosis
After Osmosis
Pressure
Reverse Osmosis
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Reverse Osmosis (RO) Water
Treatment Systems