Reverse osmosis and water purification

The purification of drinking water consists of a series of steps to which the water is subjected to eliminate waste (solid and mineral) and microorganisms from it in order to obtain water of greater purity and better quality for the consumer.

A water purifier is an equipment or device that removes (eliminates) the impurities present in the water, considering that most of these impurities are imperceptible to the human eye. In other words, it can be said that water purifiers aim to remove impurities and organic and inorganic elements such as germs, bacteria and metals.

Up to 2000 different pollutants have been found in the mains water of large cities. For this reason, when it is required to use water for pharmaceutical, industrial, food or laboratory processes. It is necessary to know the quality of the water as an input and to be sure of the optimal characteristics for its applications.

What is the inverse osmosis?

Reverse osmosis is a technology for water purification, where a semi-permeable membrane is used to remove minerals and ions from the water, in order to remove the largest particles from the water.

This technique works by applying pressure to the water to push it through the semi-permeable osmosis membrane to filter it. This semi-permeable membrane allows the passage of some molecules or ions, through diffusion. The rate of passage will depend on the osmotic pressure, concentration, electrochemical gradient and temperature of the molecules or solutes, as well as the permeability of the membrane to each solute.

At present, water purifiers with reverse osmosis systems are used. The result of this type of water purification is that the solutes are retained on the pressurized side of the membrane, while the pure water molecules pass to the other side. This occurs thanks to the selectivity of the membrane used, which prevents the passage of large molecules through the pores, allowing only the passage of small molecules.

In conventional or normal osmosis the solvent moves spontaneously from the area of โ€‹โ€‹low solute concentration (high water potential), passing through a membrane, to an area of โ€‹โ€‹high solute concentration (low water potential).

Reverse osmosis deals with a diffusive mechanism, where separation occurs thanks to factors such as solute concentration, pressure, and water flow rate.

How does reverse osmosis work?

In reverse osmosis a pump is used that increases the pressure on one side of the membrane where the water to be treated is held. The function of this pump is to force the water through the semi-permeable membrane by osmosis, allowing 95 to 99% of the dissolved salts to be sent to the reject flow.

The amount of pressure required will depend on the concentration of salts in the water that feeds the system, the higher the concentration, the more pressure will be required to overcome the osmotic pressure.

Thus, two water flows are obtained from the result of the filtration by osmosis. One of the filtered water and one that represents the flow of water that carries the concentrated contaminants, which did not pass through the reverse osmosis membrane.

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