Definition of Reverse Osmosis

Osmosis is a natural process by which a solvent flows through a membrane from an area of ​​low concentration to an area of ​​high concentration. When carrying out this physical phenomenon, an osmotic pressure is generated, which must be overcome if the The process is to be done in reverse, from an area of ​​high concentration to an area of ​​low concentration. concentration. That is, if the pressure is increased in areas of high concentration and the osmotic pressure is overcome, the water is able to cross the membrane and be obtained in a purified way in what is called permeated.

Advantages and disadvantages

Basically, this process has an efficiency of between 93% and 98% depending on the system and its recirculations. These efficiencies are high for the type of technology and process and, in addition, it has the advantage that the equipment is usually compact and automatic and energy consumption is much lower compared to other water purification processes such as distillation. Furthermore, while 100% virus removal and

bacteria, many bacteria that cause serious diseases are retained with this technology.

Like any technological process, there are also disadvantages, such as the fact that the membrane wears out and must be cleaned or replaced. It is also considered disadvantageous that the water obtained is of quality demineralized, so, depending on the equipment in question, it is often not suitable for consumption human. In addition, it is a technology that is typically combined with others to increase its efficiency in the softening and purification process, for example, the previous use of filters. In this same sense, a treatment for the reject water must be reviewed and defined, since it is highly concentrated in you go out, ions and contaminants.

On the other hand, this technology is used to remove ions, molecules and also suspended solids. Ions such as sulfates and nitrates will be retained in the membrane while organic matter has less efficiency in its retention as well as gases dissolved and electrostatically uncharged molecules. That is, the rejection of contaminants also depends on the size and the load.

Domestic and industrial equipment

Reverse osmosis equipment, in general, have filters that will retain grit and suspensions before the water passes through the pump. Then the fluid is pushed towards the membrane by means of a pump that raises high pressures, since it must overcome the osmotic pressure and, therefore, Finally, the water passes through activated carbon filters that have the function of eliminating impurities and giving the characteristics of colorless and odorless The rejection can be discarded with the required treatment or recirculated with new waste water. feeding to increase the efficiency of the process.

Now, the passage of the fluid through the membrane is carried out in a particular way and not as a simple filtration. This undergoes radial diffusion when passing through concentric membranes, which is why the permeate is collected by the central part of the tube containing the membrane while the concentrate is collected by the side. In this sense, the efficiency of the process in terms of water purification will depend on the osmotic pressure, the concentration of the feed water, the force driver or electrochemical gradient of the process, the temperature and the permeability of the membrane, its selectivity in terms of solvent and solute as well as the degree of exhaustion that it has.

Reverse osmosis membranes require cleaning at defined intervals depending on the requirements of the process and the quality of the material. feed water (as well as previous processes such as filtrations, microfiltrations, passing through granular activated carbon filters and the rest). Manufacturers suggest monitoring the efficiency of the process and when a 15% increase in salts in the permeate is observed, the need for cleaning is identified.

Depending on the contaminants that the membrane has, cleaning of different pH values ​​and different water flows, temperature and others will be required.

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